Were the 1990s colors for the Strat Plus and American Standard Strat the same?

Short answer, no. Lots of overlap, but I don't recall the two lines ever having the exact same color offerings.

I'd search around and look for old issues of the Fender Frontline. During those years it was a much smaller thing than it would become in the early 2000s, but I remember them as early as '93-'94, and I know they weren't new then. That SHOULD give you some direction.