I recently went to Essendon where the refueller would not give me AVGAS until the aircraft (hired) had red AVGAS stickers stuck on next to all the tanks. Thankfully he had some in his truck!
I'd rather have that refueler than the one who commenced filling my piston engine machine with Jet A1 until he noticed the red Avgas stickers. (Yeah, it was my fault, I wasn't supervising the fueling, normalisation of deviation.)