The only
paint I've found that works on PVC or Hypalon is Krylon Fusion
Paint.
Order online or sometimes Wal mart has it.
I clean the surface first with Acetone. Acetone is tricky and may damage patch's,
repairs and other attachment and sealing points, and some fabrics and surfaces so beware. Be very careful with it.
The second trick to Krylon Fusion is a very thin coat bites to the surface better.
Just barely enough to cover.
Jus' my 2 cents worth.