It's a difficult problem if you want to get the colors correct. Of course, the dash is still a different color, and the top of the dash (if there is no dash pad) is still another color. Not easy to match from samples, as red often fades badly.
I have seen a '64 GM book with paint chips and color codes that also had color codes for interior colors. Of course, the problem is is that they are codes for old Dulux or PPG paints which aren't being mixed anymore, so that's out.
For my '62, I just matched the dash and interior trim colors to the original ashtray, which seemed to be the least faded paint on the dash. I had a dash pad, so the unique, glare less finish of the top of the dash wasn't an issue. As my car was a 400 series, the steering wheel was two-toned, and had to have a light color match for the inserts on the wheel. Not easy to do. I changed the exterior color of my vehicle from original, but I wanted the interior colors to match original and have original upholstery.
Super interested in other members who have faced the same problem and where they have gotten their paint codes, or better yet, how they were mixed and with what type of modern paint.