'Ex-channel' - mighty effect for color changing. You must set WHAT yuo want to do with R G B channels. For example, if you set R=G, G=R, B=B - then green objects become red (red leefs of trees), and red objects become green (green faces). Also you can set channel to minimum (0) or maximum (255). Also you can transform red objects to yellow R=R,G=R,B=B. Enjoy =)