In our neighborhood we have two competing gangs:
Supposedly before European settlement of North America the black variant was more common. It had better cover in the deep virgin forests you see. J.R.R. Tolkien was thus zoologically spot on to put black squirrels into Mirkwood forest, where they added not the note of mirth that squirrels can manage on a good day, but another bit of somber darkness.
"There were black squirrels in the wood. As Bilbo's sharp inquisitive eyes got used to seeing things he could catch glimpses of them whisking off the path and scuttling behind tree-trunks."
Grey squirrels did well when the wilderness was cleared, but now that we are in many areas actively re-foresting the Elder Race of Squirreldom is reasserting its power. For unclear reasons the black squirrels seem to have a slight competitive edge, and at least locally are slowly pushing their rivals out of town.
By the way in England we have a three way imbroglio. The native red squirrels are being hard pressed by the invasive North American greys, who in turn are being leaned on by their sinister black counterparts.
My British friends give me a hard time about this, to which I reply; "Yes, and thank you so much for the starlings".