here is a typical 81-87 front light diagram.
looks like the colors are the same.
you should be able to go color to color.
I guessing you have checked, but have you looked to see if the '91 underhood light harness will plug into the bulkhead connector on your '86?
oh and the other thing is to make sure you ground both sides of the lights. there is a grounding lug on both sides. if you only ground one your light s will do some strange stuff.