The pale-blue 'Indiglo night light' colour is the best to use for night-time visibility. The legality of certain colours will depent on your state's laws. Some states (like Texas) permit neon and LEDs on bike while others do not. You need to check specifically for your state.
Here is a cut-n-paste of the 'primer' on colour perception from the Burgman site. How the colour of the reflected light of an object is perceived is different from how the colour of the transmitted light of a lamp is perceived:
"The reason the human eye perceives colour from an object is that the object reflects photons in a given wavelength of light and absorbs all other colours of light. A yellow ball, for instance, reflects yellow light (photons in the 575nm wavelength range) and absorbs all other colours of light.
Colour perception relies physiologically on the cones in our eyes, of which about 60% perceive red, 36% green, and 4% blue (primary light colors).
Whilst red & green pigments make brown, red & green light make yellow. Our eyes use the red & green cones to perceive yellow, thus they are using 96% of the cones and light gathering capability of the eye.
In addition, yellow is close to the midline of the spectral sensitivity of the human eye in photopic (light adapted) conditions, thus it is almost the easiest colour for the eye to see. Hi-viz yellow (that nasty yellow-green) is the easiest colour to see when the eyes are light adapted. This is why the school zone signs that are hi-viz attract your attention better than the old "school bus yellow" signs.
Now, in scotopic (dark adapted) conditions, the dark adapted eye becomes more sensitive to blue than to red as the retinal rods take over from the cones. This is known as the Purkinje shift and explains why the human eye can see so easily under an "Indiglo" nightlight. The pale blue photons emitted from the electroluminescent panel is the midline of the spectral sensitivity of the human eye in scotopic conditions. The physics of how photons are emitted from electroluminescent panels also play a factor, however the new pale blue gallium nitride LEDs can nearly replicate the colour of the photons from EL panels.
FYI - This is the primary means that an LED television works. It utilises bi-colour red / green leds to allow the human eye to perceive yellow light."