...I hate the plastic gas containers and would rather use the metal can with funnel attached.
Wait a few years and then look in the bottom of that metal can. Every one I have ever inspected carefully has at least some corrosion, and many have a lot of corrosion. I think the plastic fuel container is a great invention.
About the furthest I will deviate from always using the correct color coding is that I once had to buy a blue kerosene can instead of a yellow diesel one. I still have it and use it, but kero and diesel are very close. I don't use kero for anything, and have never bought any, so the chances of confusion are very low.