Replacing old fan with Hunter 20763.

People find all kinds of creative ways to wire things. White wires are always supposed to be neutrals and therefore should always go with other white wires, and colored wires should always be hot and should always go with other colored wires. If you have a voltage tester you could test to see if in fact the blue wire is actually the hot and the white is actually the neutral. (test each wire to a ground). If the previous fan was wired backwards, it would not affect the operation of the fan or lights at all. But you'd probably want to make sure the new fan was wired properly. In that case connect the white from the fan to the neutral and the black and black/white to the hot.