I've always wondered where the whole, blue LED is the same wavelength as the moon thing came from. *Ignoring the fact that different blue LED's are on slightly different wavelenghts* Besides being passed around from mouth to mouth, I've never found anything that actually lends the argument any weight. Since the light from the moon is light reflected from the sun, then the sun's wavelength would also have to be blue.
But the true color of light from sun is white, the combination of all visible wavelengths of electromagnetic radiation. So the majority of the light from the sun would have to be blue, with all other colors in the minority. But from what I can find, sunlight is pretty evenly divided among red/blue/and green, with the other colors combined equalling about the same area as any one of the primaries, since they are just combinations of the primary 3. So the light from the moon should also be primary divided among red/blue/and green, and not just blue.
And blue is the most easily scattered by gas molecules in the atmosphere, giving us our pretty blue sky. And since the atmosphere is the same at night, the light from the moon should also lose much of its blue wavelength to it, leaving the light primarily red/green.
But the primary visible light at any given time is based on the angle of the light source to the atmosphere over whereever the observation is being done. FI when the sun is on the horizon, the light is passing through more of the atmosphere which scatters the longer wavelengths more, resulting in the sky's reddish/yellow color. The same holds with the moon. The only time the light from the moon looks white, is when it essentially directly overhead, allowing the light to pass straight through the atmosphere with limited deflection, otherwise it tends to shades of yellow.
Anway, as best as I can tell you should be able to use any color of LED and get to be just as close to moonlight as blue. Personally, I use blue because I like the color it gives the tank, but that's just my taste.
