Changes the color modulation of an object. This is a color value which is multiplied with the object color.
RGB(255,0,0) will only let the red part of the color show.
RGBa(255,255,255,128) will make all color half transparent (unless alpha addition is disabled in the graphics options).
SetClrModulation(RGBa(128,128,255,128), GetCursor());
Colors the selected clonk of the first player slightly blue and makes him half transparent.