Because there’s a strong relationship between the types of light we see and the temperature of the body that emits light, our eyes perceive bluer lights as correlated with daytime (under normal circumstances) and predominantly redder lights as suitable for times closer to dawn/dusk, or even during the night.

That’s why blue, night-vision-ruining headlights are so obnoxious on the road; they’ve got the wrong color spectrum for a night environment.

That’s also something that many household lights struggle with: their spectra make it difficult for your body to adjust, particularly at night. Whereas the old incandescent bulbs often ran at a low, night-suitable temperature, many of the fluorescents more common today emit bluer light, and contribute to people’s ubiquitous difficulties in getting to sleep.

Astronomers and backpackers have figured this out; if we don’t want to ruin our night vision or mess up our body’s night/day internal clock, we would do well to change the color/temperature of the light we use after dark. That’s why many experienced backpackers and amateur astronomers use exclusively red lights after the Sun has gone down.

But what about our computer screens? Unsurprisingly, the colors our computer monitors emit — and this includes phones, tablets, laptops and desktops — are by default optimized for daytime use. But like most of us, I use my computer just as much after dark as I do during the day. Furthermore, too much staring-at-the-screen sometimes gives me headaches, and with NaNoWriMo coming up, it looks like I’m in store for even more.