Stock speaker wire +/- question

I cannot find the Metra 72-7800 locally at a CC or BB and don't want to wait for shipping so I was going to splice into the speaker wires. In the back I have yellow & brown on the pass side and red & brown on the driver side. Anyone able to tell me which is + and - ? If anyone knows the answer for the front doors that would be appreciated too. Thanks in advance

Can't you tell which is which by looking at the stock speakers? i.e. are the terminals on the stock speakers marked? In not, I would guess brown is the negative since it's the common color.

When the positive side of a 1 1/2 V AA battery is connected to the positive terminal of a speaker (and the neg bat terminal to the other speaker terminal), the speaker will move forward (outward). This is a quick definitive test to determine which speaker terminal is positive. The OEM wire that connects to this positive speaker terminal is therefore the positive speaker wire. Simple.

there are no markings on the stock harness or speaker to indicate +/-.

I finally found a Best Buy that had the harness adpaters in stock so I picked them up....was the path of least resistance.:D