The way I paint them, goblins are usually yellowish in color. There has been a strain of reddish goblins, which tend to be larger and smarter (no actual stat changes), which may be a missing link between goblins and hobgoblins (a term that comes from robin-goblin). Of note is the fact that blue is the goblinoids' color for mystical power. Psionic goblins are all-blue, and arcane and psionic hobgoblins have patches of blue skin and fur.
Hobgoblins hold blue dragons in highest regard, and hibgiblin clans that live close to a blue dragon for a few generations eventually see the birth of a half-blue dragon/half-hobgoblin (complete with a massive horn in its forehead), which is treated like some child of prophecy and grow to lead the clans in some military endeavour.