But why do the chemtrails always have a colored glow and the normal contrails have a pure white reflection?
First, it's important to note that in the (recent) common internet meme...."chem"trails do NOT exist. They are a misconception at best, and often promoted by some who wish to continue the myth...thus, these people might be deemed "hoaxers".
Second, as to the 'colored glow' (not sure what that means, but I will hazard a guess):
Since ALL contrails are merely clouds (cirrus-type, in this case) AND can exist at various altitudes, usually (most cases) above about 27,000 feet...at certain times of the day, when the Sun is low on the horizon (mornings, evenings especially) these clouds (contrails) can be illuminated just like other clouds, by the refraction of the Sun's light, through the atmosphere.
This is why, if you notice, on occasion say....at sunset if there is a "deck" of clouds, they seem to be illuminated at the lower end of the visual light spectrum. Orange, red mostly. It is related to the height of the clouds, the angle of the Sun (compared to the observer's physical location.