Color:

What is color?

The Physiology of Human Vision
color.pdf

Color and Culture
http://www.colormatters.com/brain.html

Basics Color Theory:
http://www.colormatters.com/colortheory.html

Basic Digital Color Information:
http://www.arts.rpi.edu/%7Eruiz/IMAGING/color.html

Digital Color Theory:
http://www.kodak.com/US/en/digital/dlc/book3/chapter2/index.shtml