The honeycomb is there to serve two purposes------separate the layers of fiberglass, which is how the strength is obtained, and do it with minimum weight.
The color is probably due to wet layup resin being different than the resin in the prepreg (short for "pre impregnated").
The honeycomb and prepreg are used for high strength layups, done in a mold that is vacuum bagged, and heat cured in an autoclave.
Wet layups are heavier, and have less relative strength.
