There are 16 standard HTML colors that you can call by name. They are:
aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, and yellow.
In addition, you can create virtually any color using hexadecimal RGB values. As explained by Taylor (1998), haxadecimal numbers rangle from 0 to 9 and also use A, B, C, D, E, and F to represent larger numbers. Instead of base 10, our regular numbering system, hex uses a base-16 numbering system, so in hex A = 10 decimal, B = 11 decimal, C = 12 decimal, D = 13 decimal, E = 14 decimal, and F = 15 decimal. 1B hex is 1 x 16 + 11 = 27 decimal. FF, therefore, is F x 16 + F, or 15 x 16 + 15 = 255 decimal.
When used to represent HTML colors, hex numbers are always preceeded by a pound (#), and the first two digits represent the red value, the second two are green, and the last two are blue, so #FF0000 is full red. Here are some more examples:
#333399, #9D1424, #AAAAAA, #7A0B73, #A1100B, #336600, #CC9900