Kenshin3

I wasn’t sure where to post this but my grandma has a 560 SL that she wants to put a new stereo in however I’m not sure what wires are what on the original harness and didn’t want to just go trying stuff and so I figured I’d see if anyone knows where I could find a diagram to help me out or if anyone has done this before and could give me some advice. I mostly just need to find out which of the two red wires are constant and which ones on a switch I already found the speaker wires. Any help would be appreciated