Cloford has a useful page listing over 500 colors by color name, hexadecimal value, RGB value and Microsoft Access code number.
You cannot specify these colors in HTML and CSS by their color name but you can use their RGB hexadecimal value, eg:
<font color="#800080">
and in CSS you can also use their RGB decimal values, eg:
P { rgb(128,0,128); }
For details of color names you can use in your HTML and CSS code, see the section on named colors.