In CSS, a color can be specified in several ways:
where RR (red), GG (green) and BB (blue) are hex color numbers ranging between 0 and FF.
e.g. color: #ffffff; /* pure white */
Where each parameter (red, green, and blue) can be an integer between 0 and 255 or a percentage value (from 0% to 100%).
e.g. color: rgb(255,0,0);
Full list of the Extended color keywords supported by popular browsers (W3.org)
e.g. color: red;
In addition to the above there is a new RGBA color format, only supported by more recent web browsers (IE9+, Firefox 3+, Chrome, Safari, Opera 10+):
An RGBA value color
The alpha channel specifies the opacity of the object, a number between 0.0 (fully transparent) and 1.0 (fully opaque).
RGBA sets the opacity value only for a single element. unlike opacity which sets the opacity for an element and all of its children.
To deal with older browsers that don't understand RGBA, specify a simple color as a fallback before the RGBA rule:
This is a line of sample text we can apply CSS colors to. The background color will also affect the perception and readability of color text.
(CSS 1) Browser Support: All major browsers.
“Speed kills colour... the gyroscope, when turning at full speed, shows up gray” ~ Paul Morand