Hi Drake. I have the GGG Helio LED buttons. I have 20 buttons lit (60 LEDs) so I needed two LED controllers, the LED Wiz specifically. Each button will have 3 outputs as you said, a RG&B. With the correct software, you CAN have mame light up buttons with the correct colors depending on the game selected (or not lit). As others mentioned, for the Helio buttons they each use 55ma at max power (times 20 buttons times 3 led's each = 3300mA or 3.3 Amps) and this required me to have an external power supply (basically just a wall plug that gets spliced into the hardware, I got one that was rated for 4 Amps). I will admit it was a huge pain to set up! Took like 7-8 hours from start to finish. I also had the help of my brother who knows more about electricity than I do, so that helped.
Anyhow, it was very worth it, the end result is really cool. After all, its a labor of love, right?....... right?
I hope this helps. If you have any questions i'd be happy to help
As you said in your last post, if you are keeping the maximum power consumption per board under the 500mA maximum then you shouldn't need an external power supply.