In the Summer of 1999 I have experimented with programming COP's (Composite OPerator) for Side Effects' Houdini. These experiments are based on two siggraph papers [Turk 1991, Witkin 1991].
What I did, was use three chemicals as the input for the iterative reaction diffusion loops: Red, Green and Blue. It needed quite a bit of tweeking, since one of the color channels always ended up either fully zero (black) or one (white). Even in the finished COP I wrote for Houdini, the setting of input parameters is critical. One of the colors always seems to dominate, so I made that a choice in the parameters (dominant color).
And yes, since it is an iterative process that takes at least a hundred iterations to start forming patterns, my Reaction Diffusion Cop worked pretty slow. Nevertheless, I did experiment with using it for animation a bit.