different companies use DIFFERENT colors to distinguish their grades of fuel!!! ASK the guy at the service station WHO makes his gasoline and you can tell if you are getting ripped off or not... Just pump a little into a coffee cup ( try and NOT use plastic) and look at the color... THERE are ONLY A FEW refineries wherever you are riding.. BP uses CLEAR and so does MOBIL for their SUPER UNLEADED and guys like marathon and citgo use BLUES and PURPLES!!!! IF ITS YELLOW or ORANGE,,, chances are YOU GOT RIPPED OFF!!!! YES, there are different coupling devices for different fuels,,, but ONLY IN THE AVIATION sector!!! 99% of filling stations use the SAME KIND of coupling (providing its vapor recovery)... Small towns and small stations use camlock fittings!!! DANGEROUS and PROBABLY ILLEGAL nowadays!!!