I have never heard of a blue light -- I have seen purpleish heat lights.
I have used red and black heat lamps, and they are supposedly similiar to moonlight for a snake, and they can't really see them. Therefore, if you need the lamps for heat, you can use them 24/7 and should have no negative impact on the snake.
You could also look into a CHE (ceramic heat emitter). I have never used them, buy they supposedly last much longer than bulbs (therefore more expensive as well). They give off no light, just heat.