most LED's are a blue semiconductor with a phosphor layer (or multiple layers) to create different colors.
layer anything on top of light and you're going to have a reduced output, and since blue is the original underlying color of the majority of LED's, it is the brightest.
now there are newer technologies used to create colors in different ways, but you wont find these in leds that you get from ozonium or radio shack.
so the average car guy is going to use these LED's, with blue being the brightest.
but thanks for the objective input
