Thanks for the response and verification.Looks like its based on the normal fan motor wiring:
In this case, Red is +, Black is GND, Blue is PWM speed input. FG is the tachometer output so you can measure the actual speed output (its going to be a pulse train back out). I'd tie the yellow wire either GND to make sure it spins in a defined direction and won't flip on you.
Probably using some variant of a fan controller:
I didn't realize they had PWM controlled pump heads _with_ speed output, which is very nice when you want to spin them faster as it will probably be much quieter than a stepper.