Answer:
As color is simply the kind of light reflected by surfaces(if the sun was green, many plants would die), color can be explained fairly simply to a blind person. Each color represents a separate wavelength, and objects that reflect these wavelengths show up in various colors. Thus simply state the following: The color blue is displayed by all objects that reflect wavelengths from 380 and 500 nanometers.
Hope it helps <3
p.s. I know this is supposed to be kind of philosophical, but I'm a nerd, so...