I've designed a hotend for deltas that allow color switching (and to some extent blending).https://www.youtube.com/watch?v=tdA65HTppWA
The goal is to allow anyone to use this on their printer for a wide color choice.
It seems quite easy to generate at least cyan, magenta, yellow, green, blue, red and a murky sort of brown...
I am working on the color changeover and blending though.
If everything works out as planned I will also make a 4 and 5 version for CMYK and WCMYK.
It should be possible to fabricate the design and sell it for less than $70, hopefully much less.