What I noticed from the movie is that beside the head... there's nothing truly different.
And still, Pussyface had somehow a different head shape too compared to Anytime even if it's closer to it than the PREDATORS noobish from Roberto.
What tell us the movie:
-Nolan states that the 'Super' type predators are larger and rules the smaller somehow with this sort of war (anyway it tried to say they are more badass).
What show us the movie:
-3 Predators hunting 8 people... 2 people survived, all of the super were killed.
-The 3 Super dude never shown smart move. They were most of the time dumb.
-Nolan had mental issue.
What show us Predator:
-1 Predator killed 6 men + destroyed an helicopter and killed the people in. Only Dutch survived.
-Until blain death where Mac made him bleed he never committed a mistake.
My conclusion (Personal opinion, right to disagree but it'll still... be mine):
The Super Predators never appeared to be 'larger' than the original. Even more, compared to Anytime vs. Dutch close sequence and Royce vs Berzerker or Hanzo vs Super, they seems even smaller (big lol).
Also, the original vs super predator scene show it perfectly, they share the exact same size (I guess all the guys involved in the movie never tried to put logic. After all, art can be without logic nah?).
About Nolan case, I don't know if he's schizophrenic, mental breakdown or whatever (and I honestly don't care) but he's some trouble minded dude and somehow like to 'make-up' story.
He's some kind of nice story teller to get close to people for killing them after so I wouldn't take his words seriously.
My opinion about the Super:
A bullshit, it's hollywood after all and it's a fashion since years to say that in a sequel you 're-invented' the genre while the movie show us it's a poor copy/paste with the intention of adding more badass element that will beat or arrived at the same status as the original while... it's crap.
So I would say yes for the skin colour, it's just a matter of 'minor' differences between individuals who belongs to the same specie. It's not a sub-specie, just a... let's say it was just nothing and we're dealing with normal Predator here (just remove nolan quote from the movie and everything becomes clear).