Computers vs sleep: The current theory is that too much blue in artificial light causes the brain to think it's daylight. There's software out there which changes the colour balance for computer monitors, which helps redress this: I forget the name of the MS-Windows product, but what I use with Linux is called redshift.

There's a similar blue caste to LED lamps; manufacturers do this because it makes the lights look brighter than they really are. LED lamps with a redder output may be available, and are worth looking for if you're intending to read in bed to help send yourself to sleep.

Hope this helps, Stilly.