DREAMGIRLS has some to do with the thinly veiled "Supremes," but that is not its primary focus. It is first and foremost a "backstage story." It is also a story of "love" backstage, family, changing time and racial modes, etc...........
The original production was very much a celebration of Michael Bennett's genius and every drop of theater razzle dazzle that had been invented up to that point and some that was invented for DREAMGIRLS. You can certainly know "absolutely nothing" about the SUPREMES and think DREAMGIRLS is the best musical you will ever see in your life.
Having read a couple of books about Diana Ross and Mary Wilson's book, I would say there are reflections or inspirations of the SUPREMES in DREAMGIRLS, but DREAMGIRLS certainly does NOT represent an actual story of the SUPREMES or any actual events in their lives. Of course, DREAMGIRLS is centered around a group of black female singers and begins in the early 1960s--So of course there are going to be parallels drawn to the SUPREMES--I think simply because the SUPREMES was the most famous and enduring of the "black girl groups" of that time.
I think DREAMGIRLS is one of the greatest musicals we have ever had.
"Blow out the candles Robert and make a wish. Want something, want SOMETHING."