I think a "color blind" person could still tell those apart. I am not, but I know several who are and have talked to them about this. (Not the gas/diesel thing, but colors in general). If the cans were red/green or blue/purple that might be a problem, but I think they could tell the diff b/w red and yellow.
Great one! However, this method doesn't always work. I tried to get a 1,200 lb bull with 5 foot wide horns through a 3 foot wide gate last night, we ran through a couple sets of batteries in two hot shots over the course of almost 3 hours.

The dang thing wouldn't budge. Weirdest thing I've ever seen. However, in theory, a little electricity goes a long way.