Removing color

Alrighty guys, you were very helpful with my snow layers...now I have a question regarding getting the icons under 40K. Now, I was told all about optimization, and I did that...but somehow someone "took out color" on another board, and I'm not sure how to do that. The icon looks the same to me, but no matter what *I* do, it's still over 40K. I have PS CS2 with Image Ready.