<color> - CSS: Cascading Style Sheets 编辑

The <color> CSS data type represents a color in the sRGB color space. A <color> may also include an alpha-channel transparency value, indicating how the color should composite with its background.

A <color> can be defined in any of the following ways:

• Using a keyword (such as blue or transparent)
• Using the RGB cubic-coordinate system (via the #-hexadecimal or the rgb() and rgba() functional notations)
• Using the HSL cylindrical-coordinate system (via the hsl() and hsla() functional notations)

Note: This article describes the <color> data type in detail. To learn more about using color in HTML, see Applying color to HTML elements using CSS.

Syntax

The <color> data type is specified using one of the options listed below.

Note: Although <color> values are precisely defined, their actual appearance may vary (sometimes significantly) from device to device. This is because most devices are not calibrated, and some browsers do not support output devices' color profiles.

Color keywords

Color keywords are case-insensitive identifiers that represent a specific color, such as red, blue, black, or lightseagreen. Although the names more or less describes their respective colors, they are essentially artificial, without a strict rationale behind the names used.

There are a few caveats to consider when using color keywords:

• HTML only recognizes the 16 basic color keywords found in CSS1, using a specific algorithm to convert unrecognized values (often to completely different colors). The other color keywords should only be used in CSS and SVG.
• Unlike HTML, CSS will completely ignore unknown keywords.
• The color keywords all represent plain, solid colors, without transparency.
• Several keywords are aliases for each other:
  • aqua / cyan
  • fuchsia / magenta
  • darkgray / darkgrey
  • darkslategray / darkslategrey
  • dimgray / dimgrey
  • lightgray / lightgrey
  • lightslategray / lightslategrey
  • gray / grey
  • slategray / slategrey
• Though many keywords have been adapted from X11, their RGB values may differ from the corresponding color on X11 systems since manufacturers sometimes tailor X11 colors to their specific hardware.

Note: The list of accepted keywords has undergone many changes during the evolution of CSS:

• CSS Level 1 only included 16 basic colors, called the VGA colors as they were taken from the set of displayable colors on VGA graphics cards.
• CSS Level 2 added the orange keyword.
• Although various colors not in the specification (mostly adapted from the X11 colors list) were supported by early browsers, it wasn't until SVG 1.0 and CSS Colors Level 3 that they were formally defined. They are called the extended color keywords, the X11 colors, or the SVG colors.
• CSS Colors Level 4 added the rebeccapurple keyword to honor web pioneer Eric Meyer.

transparent keyword

The transparent keyword represents a fully transparent color. This makes the background behind the colored item completely visible. Technically, transparent is a shortcut for rgba(0,0,0,0).

Compatibility note: To prevent unexpected behavior, such as in a <gradient>, the current CSS spec states that transparent should be calculated in the alpha-premultiplied color space. However, be aware that older browsers may treat it as black with an alpha value of 0.

Historical note: transparent wasn't a true color in CSS Level 2 (Revision 1). It was a special keyword that could be used instead of a regular <color> value on two CSS properties: background and border. It was essentially added to allow developers to override an inherited solid color. With the advent of alpha channels in CSS Colors Level 3, transparent was redefined as a true color. It can now be used wherever a <color> value can be used.

currentcolor keyword

The currentcolor keyword represents the value of an element's color property. This lets you use the color value on properties that do not receive it by default.

If currentcolor is used as the value of the color property, it instead takes its value from the inherited value of the color property.

currentcolor example

<div style="color:blue; border: 1px dashed currentcolor;">
  The color of this text is blue.
  <div style="background:currentcolor; height:9px;"></div>
  This block is surrounded by a blue border.
</div>

RGB colors

The RGB color model defines a given color according to its red, green, and blue components. An optional alpha component represents the color's transparency.

Syntax

RGB colors can be expressed through both hexadecimal (prefixed with #) and functional (rgb(), rgba()) notations.

Note: As of CSS Colors Level 4, rgba() is an alias for rgb(). In browsers that implement the Level 4 standard, they accept the same parameters and behave the same way.

Hexadecimal notation: #RRGGBB[AA]

R (red), G (green), B (blue), and A (alpha) are hexadecimal characters (0–9, A–F). A is optional. For example, #ff0000 is equivalent to #ff0000ff.

Hexadecimal notation: #RGB[A]

R (red), G (green), B (blue), and A (alpha) are hexadecimal characters (0–9, A–F). A is optional. The three-digit notation (#RGB) is a shorter version of the six-digit form (#RRGGBB). For example, #f09 is the same color as #ff0099. Likewise, the four-digit RGB notation (#RGBA) is a shorter version of the eight-digit form (#RRGGBBAA). For example, #0f38 is the same color as #00ff3388.

Functional notation: rgb[a](R, G, B[, A])

R (red), G (green), and B (blue) can be either <number>s or <percentage>s, where the number 255 corresponds to 100%. A (alpha) can be a <number> between 0 and 1, or a <percentage>, where the number 1 corresponds to 100% (full opacity).

Functional notation: rgb[a](R G B[ / A])

CSS Colors Level 4 adds support for space-separated values in the functional notation.

HSL colors

The HSL color model defines a given color according to its hue, saturation, and lightness components. An optional alpha component represents the color's transparency.

Many designers find HSL more intuitive than RGB, since it allows hue, saturation, and lightness to each be adjusted independently. HSL can also make it easier to create a set of matching colors (such as when you want multiple shades of a single hue).

Syntax

HSL colors are expressed through the functional hsl() and hsla() notations.

Note: As of CSS Colors Level 4, hsla() is an alias for hsl(). In browsers that implement the Level 4 standard, they accept the same parameters and behave the same way.

Functional notation: hsl[a](H, S, L[, A])

H (hue) is an <angle> of the color circle given in degs, rads, grads, or turns in CSS Color Module Level 4. When written as a unitless <number>, it is interpreted as degrees, as specified in CSS Color Module Level 3. By definition, red=0deg=360deg, with the other colors spread around the circle, so green=120deg, blue=240deg, etc. As an <angle>, it implicitly wraps around such that -120deg=240deg, 480deg=120deg, -1turn=1turn, etc.

S (saturation) and L (lightness) are percentages. 100% saturation is completely saturated, while 0% is completely unsaturated (gray). 100% lightness is white, 0% lightness is black, and 50% lightness is “normal.”

A (alpha) can be a <number> between 0 and 1, or a <percentage>, where the number 1 corresponds to 100% (full opacity).

Functional notation: hsl[a](H S L[ / A])

CSS Colors Level 4 adds support for space-separated values in the functional notation.

System Colors

In forced colors mode (detectable with the forced-colors media query), most colors are restricted into a user- and browser-defined palette. These system colors are exposed by the following keywords, which can be used to ensure that the rest of the page integrates well with the restricted palette. These values may also be used in other contexts, but are not widely supported by browsers. 

The keywords in the following list are defined by the CSS Color Module Level 4 specification.

Note that these keywords are case insensitive, but are listed here with mixed case for readability.

ActiveText

Text of active links

ButtonFace

Background of push buttons

ButtonText

Text of push buttons

Canvas

Background of application content or documents

CanvasText

Text in application content or documents

Field

Background of input fields

FieldText

Text in input fields

GrayText

Text that is disabled

Highlight

Background of items that are selected in a control

HighlightText

Text of items that are selected in a control

LinkText

Text of non-active, non-visited links

VisitedText

Text of visited links

Deprecated system color keywords

The following keywords were defined in earlier versions of the CSS Color Module. They are now deprecated. for use on public web pages.

ActiveBorder

Active window border.

ActiveCaption

Active window caption. Should be used with CaptionText as foreground color.

AppWorkspace

Background color of multiple document interface.

Background

Desktop background.

ButtonHighlight

The color of the border facing the light source for 3-D elements that appear 3-D due to that layer of surrounding border.

ButtonShadow

The color of the border away from the light source for 3-D elements that appear 3-D due to that layer of surrounding border.

CaptionText

Text in caption, size box, and scrollbar arrow box. Should be used with the ActiveCaption background color.

InactiveBorder

Inactive window border.

InactiveCaption

Inactive window caption. Should be used with the InactiveCaptionText foreground color.

InactiveCaptionText

Color of text in an inactive caption. Should be used with the InactiveCaption background color.

InfoBackground

Background color for tooltip controls. Should be used with the InfoText foreground color.

InfoText

Text color for tooltip controls. Should be used with the InfoBackground background color.

Menu

Menu background. Should be used with the MenuText or -moz-MenuBarText foreground color.

MenuText

Text in menus. Should be used with the Menu background color.

Scrollbar

Background color of scroll bars.

ThreeDDarkShadow

The color of the darker (generally outer) of the two borders away from the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDFace

The face background color for 3-D elements that appear 3-D due to two concentric layers of surrounding border. Should be used with the ButtonText foreground color.

ThreeDHighlight

The color of the lighter (generally outer) of the two borders facing the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDLightShadow

The color of the darker (generally inner) of the two borders facing the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDShadow

The color of the lighter (generally inner) of the two borders away from the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

Window

Window background. Should be used with the WindowText foreground color.

WindowFrame

Window frame.

WindowText

Text in windows. Should be used with the Window background color.

Mozilla System Color Extensions

-moz-ButtonDefault

The border color that goes around buttons that represent the default action for a dialog box.

-moz-ButtonHoverFace

The background color of a button that the mouse pointer is over (which would be ThreeDFace or ButtonFace when the mouse pointer is not over it). Should be used with the -moz-ButtonHoverText foreground color.

-moz-ButtonHoverText

The text color of a button that the mouse pointer is over (which would be ButtonText when the mouse pointer is not over it). Should be used with the -moz-ButtonHoverFace background color.

-moz-CellHighlight

Background color for selected item in a tree widget. Should be used with the -moz-CellHighlightText foreground color. See also -moz-html-CellHighlight.

-moz-CellHighlightText

Text color for a selected item in a tree. Should be used with the -moz-CellHighlight background color. See also -moz-html-CellHighlightText.

-moz-Combobox

Background color for combo-boxes. Should be used with the -moz-ComboboxText foreground color. In versions prior to 1.9.2, use -moz-Field instead.

-moz-ComboboxText

Text color for combo-boxes. Should be used with the -moz-Combobox background color. In versions prior to 1.9.2, use -moz-FieldText instead.

-moz-Dialog

Background color for dialog boxes. Should be used with the -moz-DialogText foreground color.

-moz-DialogText

Text color for dialog boxes. Should be used with the -moz-Dialog background color.

-moz-dragtargetzone

-moz-EvenTreeRow

Background color for even-numbered rows in a tree. Should be used with the -moz-FieldText foreground color. In Gecko versions prior to 1.9, use -moz-Field. See also -moz-OddTreeRow.

-moz-html-CellHighlight

Background color for highlighted item in HTML <select>s. Should be used with the -moz-html-CellHighlightText foreground color. Prior to Gecko 1.9, use -moz-CellHighlight.

-moz-html-CellHighlightText

Text color for highlighted items in HTML <select>s. Should be used with the -moz-html-CellHighlight background color. Prior to Gecko 1.9, use -moz-CellHighlightText.

-moz-mac-accentdarkestshadow

-moz-mac-accentdarkshadow

-moz-mac-accentface

-moz-mac-accentlightesthighlight

-moz-mac-accentlightshadow

-moz-mac-accentregularhighlight

-moz-mac-accentregularshadow

-moz-mac-chrome-active

-moz-mac-chrome-inactive

-moz-mac-focusring

-moz-mac-menuselect

-moz-mac-menushadow

-moz-mac-menutextselect

-moz-MenuHover

Background color for hovered menu items. Often similar to Highlight. Should be used with the -moz-MenuHoverText or -moz-MenuBarHoverText foreground color.

-moz-MenuHoverText

Text color for hovered menu items. Often similar to HighlightText. Should be used with the -moz-MenuHover background color.

-moz-MenuBarText

Text color in menu bars. Often similar to MenuText. Should be used on top of Menu background.

-moz-MenuBarHoverText

Color for hovered text in menu bars. Often similar to -moz-MenuHoverText. Should be used on top of -moz-MenuHover background.

-moz-nativehyperlinktext

Default platform hyperlink color.

-moz-OddTreeRow

Background color for odd-numbered rows in a tree. Should be used with the -moz-FieldText foreground color. In Gecko versions prior to 1.9, use -moz-Field. See also -moz-EvenTreeRow.

-moz-win-communicationstext

Should be used for text in objects with -moz-appearance: -moz-win-communications-toolbox;.

-moz-win-mediatext

Should be used for text in objects with -moz-appearance: -moz-win-media-toolbox.

-moz-win-accentcolor

Used to access the Windows 10 custom accent color that you can set on the start menu, taskbar, title bars, etc.

-moz-win-accentcolortext

Used to access the color of text placed over the Windows 10 custom accent color in the start menu, taskbar, title bars, etc.

Mozilla Color Preference Extensions

-moz-activehyperlinktext

User's preference for text color of active links. Should be used with the default document background color.

-moz-default-background-color

User's preference for the document background color.

-moz-default-color

User's preference for the text color.

-moz-hyperlinktext

User's preference for the text color of unvisited links. Should be used with the default document background color.

-moz-visitedhyperlinktext

User's preference for the text color of visited links. Should be used with the default document background color.

Interpolation

In animations and gradients, <color> values are interpolated on each of their red, green, and blue components. Each component is interpolated as a real, floating-point number. Note that interpolation of colors happens in the alpha-premultiplied sRGBA color space to prevent unexpected gray colors from appearing. In animations, the interpolation's speed is determined by the timing function.

Accessibility considerations

Some people have difficulty distinguishing colors. The WCAG 2.0 recommendation strongly advises against using color as the only means of conveying a specific message, action, or result. See Color and color contrast for more information.

Examples

Color value tester

In this example we provide a <div> and a text input. Entering a valid color into the input causes the <div> to adopt that color, allowing you to test our color values.

HTML

<div></div>
<hr>
<label for="color">Enter a valid color value:</label>
<input type="text" id="color">

CSS

div {
  width: 100%;
  height: 200px;
}

JavaScript

const inputElem = document.querySelector('input');
const divElem = document.querySelector('div');

function validTextColor(stringToTest) {
  if (stringToTest === "") { return false; }
  if (stringToTest === "inherit") { return false; }
  if (stringToTest === "transparent") { return false; }

  const image = document.createElement("img");
  image.style.color = "rgb(0, 0, 0)";
  image.style.color = stringToTest;
  if (image.style.color !== "rgb(0, 0, 0)") { return true; }
  image.style.color = "rgb(255, 255, 255)";
  image.style.color = stringToTest;
  return image.style.color !== "rgb(255, 255, 255)";
}

inputElem.addEventListener('change', () => {
  if(validTextColor(inputElem.value)) {
    divElem.style.backgroundColor = inputElem.value;
    divElem.textContent = '';
  } else {
    divElem.style.backgroundColor = 'white';
    divElem.textContent = 'Invalid color value';
  }
});

Result

RGB syntax variations

This example shows the many ways in which a single color can be created with the various RGB color syntaxes.

/* These syntax variations all specify the same color: a fully opaque hot pink. */

/* Hexadecimal syntax */
#f09
#F09
#ff0099
#FF0099

/* Functional syntax */
rgb(255,0,153)
rgb(255, 0, 153)
rgb(255, 0, 153.0)
rgb(100%,0%,60%)
rgb(100%, 0%, 60%)
rgb(100%, 0, 60%) /* ERROR! Don't mix numbers and percentages. */
rgb(255 0 153)

/* Hexadecimal syntax with alpha value */
#f09f
#F09F
#ff0099ff
#FF0099FF

/* Functional syntax with alpha value */
rgb(255, 0, 153, 1)
rgb(255, 0, 153, 100%)

/* Whitespace syntax */
rgb(255 0 153 / 1)
rgb(255 0 153 / 100%)

/* Functional syntax with floats value */
rgb(255, 0, 153.6, 1)
rgb(1e2, .5e1, .5e0, +.25e2%)

RGB transparency variations

/* Hexadecimal syntax */
#3a30                    /*   0% opaque green */ 
#3A3F                    /* full opaque green */ 
#33aa3300                /*   0% opaque green */ 
#33AA3380                /*  50% opaque green */ 

/* Functional syntax */
rgba(51, 170, 51, .1)    /*  10% opaque green */ 
rgba(51, 170, 51, .4)    /*  40% opaque green */ 
rgba(51, 170, 51, .7)    /*  70% opaque green */ 
rgba(51, 170, 51,  1)    /* full opaque green */ 

/* Whitespace syntax */
rgba(51 170 51 / 0.4)    /*  40% opaque green */ 
rgba(51 170 51 / 40%)    /*  40% opaque green */ 

/* Functional syntax with floats value */
rgba(255, 0, 153.6, 1)
rgba(1e2, .5e1, .5e0, +.25e2%)

HSL syntax variations

/* These examples all specify the same color: a lavender. */
hsl(270,60%,70%)
hsl(270, 60%, 70%)
hsl(270 60% 70%)
hsl(270deg, 60%, 70%)
hsl(4.71239rad, 60%, 70%)
hsl(.75turn, 60%, 70%)

/* These examples all specify the same color: a lavender that is 15% opaque. */
hsl(270, 60%, 50%, .15)
hsl(270, 60%, 50%, 15%)
hsl(270 60% 50% / .15)
hsl(270 60% 50% / 15%)

Fully saturated colors

Lighter and darker greens

Saturated and desaturated greens

HSL transparency variations

hsla(240, 100%, 50%, .05)     /*   5% opaque blue */ 
hsla(240, 100%, 50%, .4)      /*  40% opaque blue */ 
hsla(240, 100%, 50%, .7)      /*  70% opaque blue */ 
hsla(240, 100%, 50%, 1)       /* full opaque blue */ 

/* Whitespace syntax */
hsla(240 100% 50% / .05)      /*   5% opaque blue */ 

/* Percentage value for alpha */
hsla(240 100% 50% / 5%)       /*   5% opaque blue */ 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• The opacity property lets you define transparency at the element level.
• Some common properties that use this data type: color, background-color, border-color, box-shadow, outline-color, text-shadow
• Applying color to HTML elements using CSS