I think that blue light would theoretically be better, but many many people use red bulbs and find that it works perfectly fine.
I started reading into it as well, and had just decided to use a night time bulb that minimizes the amount of light coming off of it, almost looks like it’s off during the day. I’m sure my bp can still see it, but I’m assuming it’ll be less harsh for her overall. I’ve yet to try a red heat bulb so I couldn’t tell you if there are significant differences/similarities, but a blacked out night time bulb is what I use.