If Randolph's doesn't have a match, take a sample to an auto paint supply store and have them match it and supply the pigment. Then just add the pigment to your clear Randolph's. The big problem might be in finding one that's open, as they might not be "essential.". If it's electric you can shoot it in anything you want so they can supply it in lacquer. You can use their clear also with no compatibility issues.
   Type at you later,
    Dan McEntee

James,

You might want to call Randolph about matching a color. The last time I talked to them about compatibility and their tautening butyrate I believe they said they could mix a custom color. They, however, may have thought I was painting a 50 ft span aircraft and not a model, give them a call.

Steve

I dealt with Univair, the Randolph dealer in Colorado.   They mix the colors on site.  Unfortunately, I could not induce them to scan from my sample.  They just mix what's on the menu.  But they do have a higher-level parent company with a larger selection, which they will mix.

I was able to get Home Depot to scan samples and add pigment.  If you are willing to risk a few quarts of Randolph white, you might try getting HD to tint it for you.  I have done that with some success.  Worst case is a quart of dope in a slightly off color.