Some people like to use blue LEDs. I have 36 1W blue LEDs (0.2W each of actual light output) shining up at my white ceiling and it seems to work just fine. My

Some people like to use blue LEDs. I have 36 1W blue LEDs (0.2W each of actual light output) shining up at my white ceiling and it seems to work just fine. My target brightness was 0.2W per square metre. That's based on a classic melatonin suppression study. More energy did not cause a significant amount of extra melatonin suppression. Unfortunately my brightness distribution is rather poor. The blue light is on for 12 minutes every 2 hours during the day.