Running 40-60 RGB LED's

Projects General Guidance
2
  1. A wall-wart will be easier than a step-down transformer. Especially a regulated one that you can then use to drive all of the LEDs
  2. The Arduino will not be able to handle powering the LEDs, but it can control them using something like a shift register or LED Matrix display driver. Check the multiplexing sub-forum for ideas. That is where Common Cathode/Anode comes into play, as your driver will control that choice.