We've done both, the red seems to keep them from pecking at each other.
We are currently using a ceramic reptile heater. It screws into the lamp like a light bulb, we plugged it into a dimmer switch, so the temperature could be raised or lowered as needed. This seems to be working well, they chicks quiet down and night and get up with the sun.
We started out with just a regular light, but there was one little girl who was getting pecked on really bad so I rushed to the store and bought a red light and they stopped pecking her. I hope it stays that way!
I'm going to call that little chick Roxanne, because of her I had to put on the red light.