From Game Editor
The local variables r, g and b are for the value of red, green and blue in an actor's animation. First they have the value 255 (maximum = 100%). If you set r to 127 (=50%) all the red colours in the actor's current animation have got the half of the real red value. For example, if a pixel has got a red value of 255, it is 127 now. If the pixel has got a value of 63, it would be 31 now. Set all the three c variables to 0 and the actor's animation is totally black.