I still use a 250 watt red lamp and my girls are 6.5 weeks old (they are outside). Red lights are usually a bit more expensive than a white heat bulb. I have not had any trouble with aggression or pecking at all. I have heard and read chickens are more calm with the red light. What do you more experienced say?
without checking the provided link, I believe the main thought behind the red light is that it makes it harder for them to see blood. If a chick gets injured or peck and there is blood, if the others see it, they go crazy and can often kill the bleeding chick/chicken. The red light makes it so they can't see the blood as well and helps prevent that from happening.
I have used both. When they are babies I really didn't noticed any differance. The white light didn't seem to bother them. They still ate, slept ans pooped. There is a picture on my BYC Page of my brooder and light. Also, there is a BYC thread with brooders and most use white lights.