The book has 7 foot tall black humanoid aliens, that invade earth. I heard about this book and want to read it and maybe make a PC game based on it.
The height and body color both sounds like the Overlords from Childhood's End, by Arthur C. Clarke. The don't exactly "invade" Earth, certainly not violently, but they do arrive and in many ways take over the planet.
Here's Barlowe's illustration of them:
There is also some reddish on their bodies, besides the black, but it's pretty close.
C. J. Cherryh's Foreigner Universe has a colony of humans being enslaved, then emancipated and given their own island. The aliens in question are described as "seven foot tall" and "ebon skinned".
You can see them on the cover art.