CastCor

Almost all color transparency films, color print papers and color negative films use a multilayer subtractive colour construction similar to that shown above.

The uppermost layer contains a yellow dye whose density is proportional to the amount of blue light, the middle layer has a magenta dye with density proportional to green light, and the lowermost layer contains a cyan dye with density proportional to the red light during exposure.
A yellow filter layer prevents blue and ultra-violet light from reaching the two lower layers