Obviously the tank in the car must be corresponding.
My freind had the experience were the gas station attendant swapped it. They had to call a tow truck, got it in the service, and the gas station payed around $1000 in cost. The rest of the plans for the day were gone.
There is a huge cost for fuckup. I subscribe to poka-yoke philosophy of design: create stuff so that operator's mistake cannot happen/has no serious consequences.
When there is a human, there can be a mistake. Even most intelligent people make dumb mistakes like swapping two things.
The diesel handles are black, the unleaded gas are green. The leaded gas (when it was still used) was marked as red.
Aren't diesel handles usually green? Changing nozzles and receivers would cost an unbelievably huge sum of money just to protect a few dim bulbs from accidentally using the incorrect fuel.