The publicly available Colt serial numbers end in 1985.
For numbers after that, you have to call Colt.
I don't think anyone knows precisely when Colt started using the Pachmayr rubber Presentation grips, but it was shortly after 1983 when they introduced the stainless steel models.
Rubber was used almost exclusively on stainless or plated models.
I don't remember seeing rubber on regular production blued models up until the end of production.