I talked with a guy who do all the work for the big reference restoration shops. He said that the aluminium tags were used as is up to 1967 and in 1968 they started using blue for automatic and red for stick shift.
Maybe so. Now: What about gold tags? Black ones? I've definitely seen those on NOS-in-box Carter carburetors, and I think I've seen green ones and violet ones, too. Moreover, I've seen at least one blue tag on at least one NOS manual-trans Carter carb, and at least one red tag on at least one NOS auto-trans Carter carb, so I'd want to see some documentation before I'd put full weight on that guy's explanation. It's entirely possible he's right despite my seeing what looks like counter-evidence; I hardly think they'd bring the production line to a screeching halt just because the wrong colour tag got stamped and put on the wrong carb.
Besides automatic/manual, some differentiations that occur to me as possible targets for tag colour include 49-state, California, Canada, and Export—each with manual and automatic variants.
