Colors
Colors can be specified in HTML pages in two ways: by using numbers to denote an RGB color value, or by using a color name.
An RGB color value normally consists of a '#' immediately followed by a triad of two-digit hexadecimal numbers specifying the intensity of the corresponding color: Red, Green, and Blue. For example, the color value #FF0000 is rendered red because the red number is set to its highest value, FF (or 255, in decimal).
The three-digit shorthand form is converted into the six-digit form by replicating digits (#F00 becomes #FF0000). The "functional" RGB notation uses a comma-separated list of decimal or percentage values.
Each of the following style rules applies the same color (red) to the EM selector:
EM {color: #f00;} /* #rgb */
EM {color: #ff0000;} /* #rrggbb */
EM {color: rgb(255, 0, 0);} /* integer range 0 - 255 */
EM {color: rgb(100%, 0%, 0%);} /* float range 0.0% - 100.0% */
EM {color: red;} /* color keyword */
Only 16 color "keywords" (names) are defined by the HTML 4.01 standard. These colors can always be rendered correctly, regardless of the color resolution of the user's display card:
black | (#000000) |
silver | (#C0C0C0) |
gray | (#808080) |
white | (#FFFFFF) |
maroon | (#800000) |
red | (#FF0000) |
purple | (#800080) |
fuchsia | (#FF00FF) |
green | (#008000) |
lime | (#00FF00) |
olive | (#808000) |
yellow | (#FFFF00) |
navy | (#000080) |
blue | (#0000FF) |
teal | (#008080) |
aqua | (#00FFFF) |
The Cascading Style Sheets (CSS), Level 2 Revision 1 (CSS2.1) specification includes "orange," for a total of 17 color keywords:
orange | (#FFA500) |
When you use the !DOCTYPE declaration to specify standards-compliant mode, Internet Explorer 6 and later versions ignore style sheet declarations that do not comply with the Cascading Style Sheets, Level 1 (CSS1) specification. Colors specified with hexadecimal RGB values must have a leading "#" character (see the color tables earlier in this topic). Values like "FFFFFF" are ignored, instead of being treated the same as "#FFFFFF" (also known as white). This affects all cascading style sheet attributes and properties that accept an RGB color value.
