I had the same question a while back and did some research on the net about the oil cannisters. I believe the color of the oil cannister depended on which one was installed on the engine. The oil filters back then I believe were optional eguipment. There were a couple of differnt makers of then like AC. So which ever type of cannister the dealer was using would be the one installed on the truck or car. But it has been a year since I did the research and I don't remember everything i found about them.