Again I make my suggestion to paint and over spray onto the batteries.
Way easier than worrying about it. RED for Positive.
On my coach the house batteries I replaced the positive wire so it is RED, big, heavy, and RED, the negative is Factory original black,,, (The factory original on the positive side was black as well but,, well it's a complex hookup.. I'm into Rube Goldburg.. Shore HEAVY cable runs from batteries to generator fuse block.. Factory lead moved to fuse block. On the chassis battery I did something like that too 3 positive wires became one)