Right. So. On Mars in Young Justice there are four castes.
White Martians are looked down upon. Not really seen as evil, they're more or less just considered 'lesser' beings. Basically the same as being black in the states back in the forties.
Green Martians make up the majority. J'onn, the Martian Manhunter, is one of these. As are M'gann's parents and all but one of her thirty-nine siblings.
Red Martians are the ruling class. In an earlier episode of Young Justice, it was brought up that the Red Priests of Mars are also capable spell casters.
Yellow Martians are an outlier. A sort of side-caste. There are no natural births of Yellow Martians, instead there is a ritual that will convert a Martian of any other color into a Yellow. These are the spiritual leaders for most of Mars. We know that, at the least, they preside over things such as weddings and are noted to be the typical spellcasters.
From what else we know, the Martians can also 'feel' if one of their own is wearing a different shape and may have some level of awareness as to a fellow Martian's true form. This was brought up in the episode in which M'gann is working with her family to prepare for her wedding with Connor.
Whether or not there is any actual difference among the castes, I genuinely do not know. J'onn is considered to be a decently powerful psychic among his people and M'gann is, according to J'onn, far more powerful than he is.