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Go get a "test light probe" from Autozone or the like. You can put one end to ground (clip it on to the door jam) and then test each wire in the console. With the key off and it lights up it is a constant. Use that for the radio memory. Turn the ignition on and then test around and find one that only turns on with the key on, there ya go for main power.
I have 2 red, but they are maybe 1mm2 and the ground is maybe 1,5-2mm2. I would have thought that tha main powersupply would have a larger cross section?
Get a volt meter and learn how to use it before you do damage.
I have one, and i know how to use it- but I have to wait due to another project before I can connect the battery. Just found it odd that the red + has such a small cross section.