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.<p>My target brightness was 0.2W per square metre. That&#x27;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.<p>The blue light is on for 12 minutes every 2 hours during the day.