PE,

Capstaff's patents for his two-color process call for an "acid dye (preferably the salt of a sulfonic acid)", US 1196080; US 1315464. Only the dyes which you cited fit this description: lanafuchsin & quinoline yellow. The dyes carmine and indulin blue clearly are not sulfonic.

Pinatype dyes were used to dye the planographic matrixes over and over again. The matrixes could produce as many as twenty prints. The presence of aniline groups in indulin blue and the lack of SO3 groups in it and carmine indicate that these dyes diffuse more readily out of gelatin than dyes with more SO3 groups, groups which would have the effect of binding more substantially to the gelatin.

The Capstaff process was for "one off" assemblies of transparencies. While a dye transfer to blank paper over a period of ten to fifteen minutes would preserve the highlights, Capstaff required that the gelatin be thoroughly dried before dying, (Wall recommends drying for as long as three hours). A print surface so dried would be harder and much more likely not to absorb dye in the tanned highlights; even dyes with more affinity for gelatin such as salts of a sulfonic acid. It is possible that a wide variety of azo dyes which are salts of sulfonic acids would work in the Capstaff process. So a set of dyes suitable for DT and DB might be found.