How did old hand-drawn animation achieve such consistent color?

Question

Mainly wondering how they avoided discoloration or the presence of brushstrokes. Thanks!

Found in Technology.

Answer 1

Also the paint colors were available in slightly different variations to accommodate the layering of animation cels.

If a character had a blue jacket for instance the blue would be Blue 0. And if you were going to animate just the characters arm. You would separate and animate the arm movements on a cel above the previous cel but if you used Jacket Blue 0 the top layered cel would shift the color of the blue layer beneath it when photographed. So you would paint the arm with a slightly different blue, a specially formulated Jacket Blue 1 to accommodate the slight color shift and in the final result the two Jacket Blue pigments would appear identical.