California does seem to have color coded handles, at least that I've always seen. Gas is black, diesel is green, and E85 is yellow. At least everyplace I've paid attention that seems to be the case.
I just bought a diesel Jetta and I am so paranoid that I'm going to grab a gas nozzle one of these days. I even almost did it on the second fill up. Never had that problem with the motorhome, but when driving a car you just go on auto pilot.
I pulled into a gas station up in the hills in California a few years ago and they didn't have a credit card reader at the pump. So I went inside and the lady told me to pump first and then come in and pay. NOBODY in California has done pump then pay in 20 years! Well nobody but this one gas station. So I went out and pumped my gas and then being on autopilot I got in the car and drove off. Luckily I remembered about a mile down the road and turned around and went back. The clerk was on the phone to the Sheriff when I walked in.