CSS Colors
There is a giant list of color names you can use in CSS, but people generally use a hex code. A hex code is a set of three numbers between 0 and 255 in hexadecimal (base-16) format, beginning with a pound sign, like: #FF00A7.
The first number is the amount of red, the second the amount of green, and the third the amount of blue. #000000 is black and #FFFFFF is white.
Luckily, you don't have to be able to read or write these colors from scratch! You can use a site like HTML Color Codes. This site has a color picker to visually select a color and get the hex code. It also has color charts and a list of color names.