what color did the interior come in

You will need to check your build tag, should be located under the hood, which will have body code, interior code, etc. Back in the day you could order pretty much any color with any color.

Normally, the car would have come with either a grey vinyl/grey striped fabric insert (European market) or grey vinyl/grey mesh vinyl insert (US market) on the seats. TMI makes a pretty good repro '65 interior in these (and other) colors. If you would like a pdf of the original color chart for 1965, send me an e-mail at vvwca@mindspring.com, and I will gladly send one along.