If you have an actual auto body supply store in your area they might be able to help.
Some of them up here still have year by year "paint chip" books
GM RPO codes got reused a lot depending not only on year but also on production plant and type of vehicle
( the great G80 differential debate is a prime example of this)
My 94 RPO paint code turns up as a canadian 95 only paint code but it is a mid 94 production Pontiac Mi truck.
The other kinda jinky problem with earlier gmt400s involves the whole transition from 1980s paper parts catalogs to 1990s microfiche catalogs and all of that getting scanned into early database internet technology.
Information that was kinda sketch to begin with didnt always make it.
And, the other factor....
TSBs
Technical Service Bulletins.
If you are going to live with a Chevy, read the TSBs
Get a library card, a lot of them have access to Chilton ( which sucks) and Mitchells
All kinds of mistakes can happen if you dont get access to GMs "oops" we screwed up files.