Green. All orcs will be green eventually.
Eh, that remains to be seen, there's no
known examples of a mag'har/Horde child in canon, and Blizzard's comment of "Fel Touched trumps everything else, so any child of a a Horde/Mag'Har will always be green" sounds kind of bullshit to me.
And for all the Horde's talk about redemption and stuff, they haven't
stopped being exposed to Fel Energy, either through use of tightly controlled Warlocks, combat against the Burning Legion, and the subsequent chain of catastrophes all over the place. They haven't really tried to flush it out of their system like the Mag'har have in this timeline, so I can see it becoming that powerful--as a physical mark of their shame from the past. The Mag'har are actually
dealing with their shame, rather then burying it like the Horde did--which lead to the problems that ended with the Siege of Orgrimmar--if you turn your back from your crimes and refuse to atone, then you just open things up for the next generation to repeat the same crimes.
And that is
absolutely the canonical Horde's primary issue--they refuse to take responsibility for their crimes and make amends--they make a few token gestures towards reconciliation, but they have too much pride to request forgiveness--and that leads to problems, because
they did some seriously bad shit, and it just educates that own young that it's
okay to do horrible shit as long as you win, or at least die trying. Thrall's problem is that he thinks more like a human then he does an Orc, and he's a sucker for "Redemption", and thus, he spread the story that Grom freed the Horde, and
kind of glosses over the fact he was the one who put them in that position to begin with.