Grey water tank construction material

Color does not indicate type of plastic. Polyethylene and Polypropylene are both in one group of polymers while ABS is a hybrid mixture. I spent over 7 years in the industrial plastics supply field. If you need to know you need to contact the MFR with VIN number and hope their records are accurate. If you need to have a crack repaired most farm/ranch communities have a person with special equipment to "weld" polyethylene or polypro. Too darned old to recall if ABS can be welded or if you need nasty glue.
Greg