There are recipes for methyl violet, (aka crystal violet), as a red sensitizer, cf. p. 255, Wall, "History of Three Color Photography," available online at:

http://archive.org/details/historyofthreeco00ejwa

Reading all of chapter VII is very informative about sensitizing emulsions. Methyl Violet has an absorbance spectrum very close to ethyl violet and chemically the two dyes only vary by substituting methyl groups for ethyl groups.