I have an oil filled radiator heater for at night in the flower room. I covered the red led on light with gorilla tape but its a few feet from the plants and has not caused any problems. The heat glow is very dim and i have always pointed it so you cant really see it.
The green light display on my titan controller is much brighter. Also has not caused problems. Only reversals I see are sensitive seed plants I caused nutrient stress. And i mean diesel crosses and the like.