Maybe I'm pretty misguided about what passes as offensive in the U.S., even though I've seen island/jungle native stereotypes criticized in the media in recent years.
But its obvious that the blue color isn't supposed to represent a blue colored character anymore than Tom Tom/Boy's hair is supposed to be yellow instead of blonde. This is an 8-bit game from 1986. Otherwise they'd have named it something like "Blueberry Boy".
Here's the original artwork from the japanese manual-

After grabbing the screenshot, I was curious how Sega would've handled the character art and desciption in the english manual, since it still predated political correctness. It turned out that the manual I found in the nearest copy of the game was an international edition.
Here's the art and descriptions-

Here are the translations-
COAL KID
CHIBICROW: Lil' Crow
Scharzes Kind: Black Child
BEBES NOIR: Black Baby
NEGRETTO: -sounds like the rest
If people still don't find it offensive then so be it. But it doesn't change what the character is supposed to be.