Blue light has gotten a lot of negative press over the last decade. The popular understanding of its effect is that light on the blue spectrum—which has invaded our bedrooms by way of our omnipresent smartphones and tablets—specifically triggers the brain to stay awake. But researchers are reexamining that theory. A study recently published in Current Biology is suggesting that it’s not so much the color of the light as much as its intensity. And, in fact, the study shows that yellow and white lights are linked to wakefulness moreso than blue light.1

The study suggests that the mammalian brain is conditioned to rest at the end of a light-to-dark cycle. In other words, as it gets darker, our brains prepare for sleep—whether that fading light is blue or not. To understand this, the researchers evaluated mice and their reactions to light brightness and color. They found that bright light of any color was stimulating, but when dimmed, blue light was actually more restful than yellow light.1

One of the researchers told the BBC that their research could mean that those “night mode” settings on smartphones aren’t as helpful as advertised. “Often what people are doing is adjusting the color of lighting or visual displays and making the screens more yellow," said Manchester University’s Tim Brown, BSc, MRes, PhD. “Our prediction is that changing the color is having exactly the wrong effect. It's counteracting any benefit that you might get from also reducing the brightness of the screen.”2


1. Mouland J, Martial F, Watson A, Lucas R, Brown T. Cones support alignment to an inconsistent world by suppressing mouse circadian responses to the blue colors associated with twilight. Curr Bio. 2019;29(12):4260-7.

2. Roberts M. What's the best colour lighting for sleep? BBC News. December 17, 2019. Accessed December 30, 2019.