I'll probably get shot for asking such a stupid question but, assuming the core and the nozzle is the same size in the donor reloads, what is the likelihood of a successful launch if red, green and blue grains are mixed in a single reload? I.e a RGB reload?
I wouldn't do it (unless you want to void warranty on your hardware, and flying at an EX launch), but I don't think there would be much of a problem. You probably won't get the effect you want though.