I’m not much of a shotshell shooter or collector, so help out if you can. I’ve always been told that 20 ga. shells will almost always be yellow and that 12 ga. shells will never be yellow, so that the two cannot be mistaken and accidentally put into the wrong shotgun. The problem being when a 20ga. is mistakenly put into a 12ga. followed by a 12ga. shell, causing a burst barrel or worse. Is there some industry standard that guides this color coding? I see all colors of shotgun shells at the range, but never a yellow 12ga., so is there some truth to this?