For starters, you need to change how the program UI works. It is confusing the way you have it now.
Either 1) You let them click a color first, then click a spot for that color (which colors that area). Then the color needs to not change when you click another color.
2) You have them click an area (which you want to become "highlighted" somehow) then click a color. Then no more changes when that event is done.
As it stands though, it is confusing to click areas and then have the color change after you have selected a color already. You need to event-ify your UI.