Oyster is the name of the white color, so it's not oyster and white. If your seats are Oyster color, they must be vinyl.
With Oyster seats and door panels and trims, you should have had a contrasting color on the dash, the kick panels, console, the carpet, and the package tray. The contrasting color could be gray, black, or blue.
So, what color is your dash? That would be the contrasting color for the other parts.
Also, what is the trim code number on your cowl tag, which is the Fisher Body tag on top driver side of the firewall under the hood. That will tell what color interior you had. The trim color code should be the first code on the second line of the tag and have 2 numbers and a letter. Like my car has oyster with gray interior, and the code is 12R. So, yours should have similar code with 2 numbers and a letter.