Help with fans. Which wires do what?

Hello everyone. I could really use some help to figure which wires do what on these fans. I pulled them out of a older broken G5 iMac. I would like to use them for ventilation in my terrariums. I had no problems wiring regular pc fans to 5v USB and 12v dc adapters but these Mac fans are not nearly as simple. I've tested so many different combinations to try and find which ones are positive and negative but none have worked so far.

There are two black wires, one grey wire, one brown wire.

Sounds like it could be zshorted or A faulty fan. I would investigate if it was me. Welcome to the Forums!