There are 3 different colors so each LED will have a resistor to on it sized to typical IF. (example- Red LED 2.0v IF=20ma. It's 12vdc so 500ohm resistor).

(12v-2.0v/.02a =500ohm). I'd then like to take the common from all the LEDs and run them through a POT to "ground".

I'm trying to figure out what size POT I need. Not only how ohms it will take to dim them down but also how many watts the POT needs to dissipate.

Thanks!