after swapping a new motor, i'm having difficulty wiring it up to my old harness.
All the same wires are present, but for the alternator, instead of the color coded

green stripe
blue stripe
yellow

wires, i instead have 3 yellow wires all bundled up in a quick disconnect

i was wondering if anyone had any ideas how to check which plug was which, or if anybody actually knew which was which

From the alternator, they are all the same.  Doesn't matter  which is which.

if you still have your old motor, you might be able to use a voltmeter set to ohms to determine which is which by comparing your resistance across the wires to your old stator.  

It's a triangle. The resistances should all be pretty much the same (for a good stator). And it doesn't matter - it's all AC, it gets rectified to DC, which way it wiggles is unimportant.

This is from a VW site, but shows the idea perfectly well. Interchange, no difference.

thanks guys haha i just went out to take pictures

I was thinking it was 3 phase ac, but didnt want him frying anything