Six colour layers paint an entire picture
Polaroid film consists of three lightsensitive layers that are activated, as red, green, and blue light is admitted. The light draws a negative in the layer like a film of silver crystals. Under each layer, there is a layer of yellow, magenta, and cyan colour, which is released by developing solution, as the camera spits out the film. Where silver has been released in the layer above, no colour is admitted. Instead, the colours of the two other colour layers combine to produce the colour of the light-sensitive layers.
In a photo of a blue sky, the light-sensitive blue layer blocks out yellow colour, whereas magenta and cyan produce blue.