need help identifying grape variety

A friend brought some grapes over for me to make wine. They were frozen and most were oxidized and somewhat brown, the others were slightly blueish grey. they were from northern michigan. When i thawed them and crushed them they had a great grapefruit smell. After fermenting i racked it off the lees tongiht, only about 3 gallons. the grapefruit taste is still there. Tastes good. I think it will turn out very good.
I think maybe they were Sauvignon blanc, but if so they should have been green. So any ideas?

Just make the wine with them and be happy.

There is really no way to tell you the variety with the information you just gave. That would be like trying to make an ID of a burglary suspect saying that the suspect is human, between 24 and 84 inches tall with hair and two arms. It just doesn't narrow things down at all.

White grapes turn brown when frozen.