The point of this project is to make a CMYK compatible 3D print method that only uses one filament to extrude with dyes. That way we can replace the current method of using 3 filaments. This will reduce the physical footprint, lower power usage, and lower wasted filament.
Diamond printer uses a single large head to mix 5 different filaments. Not quite what I thought you were doing, not as good as your direction. I actually had a similar idea to yours back in 2013. I discovered that standard PLA uses a specific type of dye that is also available for ink jet printer refilling (these refills were best when doing PCB manufacture). I actually have a full set of 100ml bottles of RGB and black inks made with the dye. I was thinking that small stepper + syringe, each connected to PTFE small bore tube, 1 per colour. A modified hot end head with 5 copper tubes into head. PTFE onto tube. Lots of problems, would inks dry up and clog with heat. Even if you got that working, STL does not support colour, no slicer supports colour. Suddenly becomes much more complex.