There is probably something to the issue of late-evening light source wavelengths and sleep chemistry, given light-reactive melatonin’s role in sleep. At any rate, if “blue light” can be avoided near bedtime, we’ll come closer to exposure to the natural wavelengths to which our brains have been accustomed and adapted for sleep.
Towards that end, I’ve installed a free software app called f.lux, and while it could be my imagination, I seem to be sleeping better. And I enjoy watching the monitor go from a pinkish cast at local daybreak to the more familiar blue cast–a subtle difference to the eye, but maybe not so much to the brain.
The folks at f.lux have done their (preliminary) homework. Read their RESEARCH PAGE or other recent articles about this below.