I used the Arduino UNO combined with three LumiGeek shields to run lighting. LumiGeek has dedicated shields to support 1 Watt RGB LEDs that require constant current, Addressable RGB LED Strip, and Non-Addressable RGB LED Strip.
Step 1: 1 Watt RGB LEDs (2x)
I wired these in series and powered them with the 12 Volt source on the Power Supply. The LumiGeek shield that powers these is the 3XCC - it provides constant current so the LEDs don't fry (the LEDs decrease in resistance as the heat up so the board manages this in order to provide a constant current).