A multi-use set of Azo dyes both for DB and DT would be very convenient. It might also be possible to combine the two processes: develop with a tanning developer, let the dye transfer into the whole matrix approximating the correct tones, and then bleach out the highlights.

From the language of the patents Capstaff seems to indicate that he uses only one dye per color. It also seems that his images from Capstaff Kodachrome were all assemblies requiring silver halide emulsions on transparent bases. I recall seeing a two-color portrait of George Eastman(?) from the 1920's which was published in the Time/Life book on photography called "Color", (1978). That gives some idea of the color values; the warm tones were somewhat orange. Looking through samples of dyes available at that time with the correct chemistry (acid dyes which form salts of sulfonic acids) it might be possible to rediscover the dyes that Capstaff used. The Colour Index gives structure, hue, lightfastness and date of discovery.

Capstaff invented two versions of DT: the first tanned the highlights with a bi-chromate bleach in the standard manner; the second tanned all the gelatin with ferric chloride and tartaric acid and then de-tanned the lowlights with a UV light image. I assume each version used different dyes. IDK which version the portrait in Time/Life "Color" used. I would love to see a Capstaff DT in the flesh.

I have seen examples of European Gasparcolor on Youtube. Gaspar moved here to California before the war and lived in Beverly Hills. He donated all his papers to UCLA and these are held by Special Collections. I wonder if he had Gevaert coat his films after the war. IDK who did that work for him.