Worqx.com offers a nice primer on colour theory. Colour is an important part of the design process since colours all have emotional meanings. And those connotations can be different for each person.
Complicating it all is the variances in monitors calibrations. I was working with a friend the other night on his graphic design project for college and I suggested he try moving the ‘lime green’ object. He didn’t know what I was talking about, because what were lime green and teal on my monitor where yellow and aqua on his.
See the “What is Red” for more discussion on the problems with determining and communicating colours.
