New decoding a fender tag thread

I have gone through the forums on decoding the fender tag and the internet with out success

I have a 66 Barracuda
Under the paint section on the fender tag it has for my car 661 (which is light mauve) next to that I have two Bs

Everything else I have found shows a space and than a B, mine has no space - 661BB

I found on a different thread, that the second B is trim paint.

Can anybody confirm what these Bs stand for?

Or point me to a site that breaks it for me? (early valiant doesn't)

thanks