Help! How do I add some color when PS is resisting me? :/

I'm needing to make the eyes green (which they are). I've tried using the polygonal lasso tool and paint bucket tool to fill the color, but when I change the foreground color to green, it automatically goes back to grey. Help! What am I doing wrong? Or can anyone have mercy on me and just make the eyes green? :)

Thank you. I use PS7 btw.

ETA...THANKS SO MUCH! Got it now! =D