I can't see how people make this mistake. When I go to fill up my wife's gasoline car, I have to press a button to select which grade of gas. A lot of diesel pumps will even have a button to select which fuel grade, even though there is only one. The pump itself will also say diesel. I have a warning label on my dash to use ULSD only. That same warning is on the fuel door. The fuel cap has "Diesel" written on it. There really is no legitimate excuse to misfuel unless the delivery guy filled the wrong tank; then there is nothing you could have done for that one.
Pump colours are different and not standard. The majority of the pumps may be green where you are, but here the diesel pumps are all yellow and the only green pumps I've seen within a few miles of my house are gasoline pumps at the Husky stations. The only legitimate gripe we can possibly have is the different sized pump nozzles (I've come across 3 so far and the truck nozzle is not fun to use without an adapter).