Cable connections to battery

[Copper]

I needed new starter batteries for my class C Kountry Star. Not all the cables are color coded for positive or negative and unfortunately it was so dark in my storage shed I didn't realize this until I came back and tried to install the new batteries. I got quite a spark from one that I was actually marked red when I touched it to the positive post.

Is there some way of finding out which pairs of wires belong together? I could separate the groups this way but unsure how to do it.

 

[Kevin D Pem]

Multi meter to frame using continuity settings. That's the ground.