I've figured out how to change the color of the particles based on a small variation in size they are given at birth. Its not the most elegant solution but seems to do the trick. here's the file for anyone interested:
www.juniortaxi.net/files/c4d/tp_network%2002.c4d
However, I have a new question that I thought i'd post here instead of starting a new thread.
Is it possible to attract particles to the luminance of an objects texture? I know its possible to create particles from an objects luminance using the PMatterWaves generator, but once the particles are fired off can they be attracted to another textures luminance.
thanks!
chris