The choice of colors is deliberately limited to those which have been available on the IBM PC since its earliest days. This is the same list of choices supported by the "color" command for setting the color of the DOS prompt. The following table shows the codes and names that DOS/Windows gives to these colors, their actual RGB values, and the nearest "websafe" equivalent. Anybody designing a website and wanting to give it that "DOS/EGA" look should pick colors from this list.

code	name	real RGB	websafe
0	Black	000000	000000
1	Blue	000080	000099
2	Green	008000	009900
3	Aqua	008080	009999
4	Red	800000	990000
5	Purple	800080	990099
6	Yellow	808000	999900
7	White	c0c0c0	cccccc
8	Gray	808080	999999
9	Light Blue	0000ff	0000ff
A	Light Green	00ff00	00ff00
B	Light Aqua	00ffff	00ffff
C	Light Red	ff0000	ff0000
D	Light Purple	ff00ff	ff00ff
E	Light Yellow	ffff00	ffff00
F	Bright White	ffffff	ffffff

Admission: in real MS-DOS, it was not possible to set the background to any of the "light" colors (8-F). This restriction has been lifted in the Windows NT/2000/XP command prompt. This website ignores this issue and freely uses #999999 as a background color. Yes, #999999 (gray) counts as a "light" color because it is technically light black. I'm not kidding; I have the first edition of Norton's Guide to the IBM PC to back me up.