If you absolutely can’t find any wiring documentation for this, you may need to open the covers to have a look / measure resistance with an ohm meter and such.
Forget about the wire color completely at this point.
The ground / 12v / ACC wires are usually 3 pins clustered together, not always, but often is, so when you find the ground, the other two are right near by. So your main focus is finding the ground, 12v+ wire, and ACC wire, that's it at this point. Once you get it powered on, the rest is much easier.
The ground wire is usually easy to figure out as it will be tied to the radio chassis and an ohm meter will show this pretty easily. So that one is usually very easy to mark with tape.
The 12v+ wire often connects to a big diode, so internally, can use an ohm meter to see which pin does this. May even connect through an inductor coil, but test it the same. The diode is for reverse protection in case it gets hooked up backwards, a lot of 12v electronics had this, and it connects across the ground wire and 12v wire on the PCB internally. If this is the same for that unit, you would then know ground and 12v+ wires.
If you can find those two main wires, you are left with the ACC wire which is needed to turn it on. This wire is almost always right next to the 12v+ power wire.
Once you get it power4ed on, the speaker wires are easy to figure out, same with remote output wire, and power antenna wire if equipped.
I had to do this with a couple cheap car stereos many years ago and is how I did it. I opened it up to help not connect 12v to the wrong wires. Finding the stereos chip-amp IC model also can help as it has a pinout and will show where the traces route to the speaker wire pins (assuming it is not some obscure chip, and datasheet is available).
Power up testing through an old car taillight bulb for current limiting. If you get it wrong and connect directly to a car battery it will go up in smoke pretty fast, the smaller 12v light bulb(s) in the 12v+ wires limit the current to minimize frying it accidentally. Without having it here I can’t say for sure, but finding what pin does what is doable, but might not be able to explain it well, and perhaps that radio might make it more difficult also, not sure. If what I typed here doesn't make sense, you might not be able to figure it out.
And of course if you do have to open it up, can trace the connector pins on the PC board to see where they go and cross reference the 12v input to IC chips / regulators and such, although not easy if you have never done that sort of thing.
