There were 4 wires in the fixture: Black, White, Red, and the ground.
I am 90% certain the black one is what was connected to the previous light fixture that was controlled by the switch, and the red was capped an unused (there is a chance I mixed that up though)
Anyway the fan instructions said for a single switch to connect the ungrounded black wire to the black and blue wires from the fan, and connect white to white, and connect all the grounds (from fan, ceiling, and ceiling bracket)
Instructions said nothing about a red wire. I googled it and most people were saying it is an additional ungrounded wire for multiple switch setups and its ok to leave it capped and unused, so that's what I did.