I keep my red foot's humidity at around 80%. My tortoise, Maui, loves it. I try to keep the cool side of the enclosure at 70 and 80 degrees on the hot side.
Ambient should be 80-85.
Hot spot: Just over 90
And a few cold spots of 75 or so
Humidity 70% min, ideal 85-90%
This is based on your typical northern red foot, but the exact care depends on what type of red foot.
Caboose,
It's difficult to emphasize how important it is to do your own research, but here are two excellent resources. One is free the other is a $30 investment but it's worth every cent.
It not only depends on your tort, but also on the ambient temps and humidity in the area the tortoise is kept. If it is in a cool but dry location, such as heavy air conditioning, then it needs higher levels to offset that since so much of the heat and humidity will be sucked out by the room.