I was born in '87, so I was barely around for Jem - BUT that doesn't stop me from thinking the show was AWESOME (thanks YouTube)!
Shana Elmsford was the synth drummer - and later guitarist - in Jem's band, The Holograms. She met her bandmates in foster care at Starlight House (the home for girls founded by Jem), which allowed her to come out of her shell, as she was a shy, introverted child. Shana designed most of The Holograms' costumes and breifly left the band to become a full time fashion designer.
Something tells me that she and Friday Foster would definitely get along.
There were other Black Female characters on Jem amongst the Starlight Girls:
There is also another fashion designer on the show - Regine.
You can find more info on each of their characters HERE.