Color Slide Film First Available Commercially?

The first modern chromogenic three-layer color film with dye-couplers
contained in the gelatin layer was the Agfacolor Neu slide film
developed under Drs. Wilhelm Schneider and Gustav Willmanns and
introduced by Agfa in 1936. These dye-couplers had fatty acid chains
attached to make them water insoluble and prevent migration into the
neighboring layer. Agfa abandoned this technology around 1980, and the
last manufacturer to use it was Orwo, which took over the Wolfen plant
in East Germany after the war.

The first three-layer color film with the current technology of
water-insoluble dye couplers, contained in small oil droplets
emulsified into the gelatin, was the Kodacolor negative film introduced
by Kodak in 1942. Today all color films are based on that principle.

Dr. Heinz Anderle, Austria