The color doesn't make a difference for warmth but 24 hour light makes them a little crazy. White is good for daytime. Red is good because it hides injuries and blood. Blue has a calming effect on chickens. The best heat source is no light at all. A ceramic heat emitter is what I use after the third day. Then I can use CFLs or other light source to create a normal day length. The ceramic don't produce light so they're more efficient. They break but not as often as regular lamps nor as messy when they do. All the pet stores carry them but they're cheaper on ebay. http://www.ebay.com/sch/ceramic heat emitter