Yeah, gasoline staining is very subtle. Look for examples around you if you can, or look at photos. I think of the 2-gallon and 5-gallon cans I have in the garage for gas for the lawn mower. They're red enamel. The effect of spilled gas hasn't really discolored the enamel over time, just left some different schmutz behind as any gas that spilled evaporated. Might be too subtle to show in small scale. But in any case, it's subtle.