Look at a few CSS files and you will see that most colors are defined using hex codes, which is a 6 character string made up of the numbers 0-9 and letters a-f. But there is also a list of CSS color names that you can use instead of a hex code.
The squares below are the 147 colors that are recognized in CSS. They're camelCased to make it easier to read, but they are case-insensitive so you can capitalize how you see fit when actually using the colors in your CSS.
All of the squares are linked to pages where you can get more information about the specific color.