The very first color images ever made by a camera were achieved using three exposures taken through blue, green, and red filters. When Polaroid set out to create their first instant color film, they built on that established tradition.
In 1963, Polaroid introduced Polacolor film, which allowed instant camera owners to take color photos for the first time (via Serbia Photo). The overall mechanics were similar to previous cameras, spreading reagent between two layers of photo paper by running them between rollers inside the camera.
What made Polacolor different way the negative photo paper was designed. Instead of a single layer, this film had three layers, each of which were sensitive to either blue, green, or red. As explained by Film Colors, Yellow, magenta, and cyan developing chemicals were pressed across their respective layers of the negative before being sandwiched together into a single image.
By keeping all of the magic inside the camera and the film, Polaroid was able to maintain a seamless user experience while bringing color to instant photography.