Quoted from CaptainNeo:
I'd like to know more about this. I may use a RGB system for the inserts on my coversion project.
There is a standard LED hardware module from pinballcontrollers that can support RGB. It just uses a two wire serial cable to connect to the P-roc/driver board chain. It uses directly wired RGB boards that easily mount under an insert. There are also break out boards available to make wiring easier. It is more wiring then a serial approach, but more reliable. When I started to play around with them, I added some code in my game to quickly tell if it is a standard or RGB lamp, so that both will play nice together. Also lets me upgrade the the lamps later without having to change code immediately. There are also RGB Flashers, but I've not played with those yet.