There was a 4th black dye added to the above mix and all 4 of them had specific ratios to prepare the correct color. The nature of the mix was determined by the spectral sensitivity of the film itself.

They dyed starch grains were applied to the varnish layer by a raking process to spread them evenly and randomly across the varnish and then the material was rolled or pressed flat under pressure that flattened the grains. The emulsion was then coated on top.

Part of this is described in the textbook "History of Color Photography".