Ok, I'm not completely disagreeing about the colored light..
Wait, I sort of am! Maybe it depends on the breeds? Temperaments? I just used a plain light bulb in my brooder, and no one ever picked. A farmer friend loaned us a lamp for the first batch, and it had a plain light bulb in it, too. Except for treat time, everyone is fairly docile with each other, and I haven't had any problems at all. Of course.. I try to run 'Peaceful Kingdom' here, so anybody pecking anyone else got a "hey, stop that!" in the first week. Hubby caught them chest-bumping yesterday morning and gave them quite a lecture about it (wish I could have been a fly on the wall for that "ladies don't act like that" speech!).
Anyway, my group is 5wks now, and their brooder box was quite large, so maybe that made a difference?
-Meghan