What gauge color is the best?
 

I know this would involve some personal opinion. But to me I find that blue, indiglos, and reverse indiglos and the like are really hard and tiring on the eyes, as with all light in the blue spectrum.

I like the red on the P5 very much since it's legible at night and easy on the eyes. The only gripe with it is that the color is washed out during sunset. I think red is used on gauges of many military planes also.