Color changes are still very slow and generate a huge amount of waste. I think that 90% of the effect can be achieved with 50% of the color swaps by interlacing colors layer by layer. So this would be a modifier that is applied to the regular painting color properties. One layer gets printed down using the base layer, but the next layer gets put down with whatever color is desired in the area that is colored.
So instead of having a black object with some grey patches, we could have a black object with interlaced white/black layers. It won’t look quite as good for some models, but it cuts the number of color swaps in half and in a lot of models you don’t necessarily need super crisp color boundaries. It also makes it easier to blend out a color when you need a smooth transition.