The tricky part is that as soon as I pause printing, I need to move the nozzle out of the way and make sure no extra material comes out so I can resume the print where I left off (after changing the filament).
Changing the filament is easy and I have a design that tolerates a fairly wide window of places to change it - I just would like to do it cleanly.
Another possibility that occurs to me is butt-splicing a second (or third) color at a known length, but I need to make something that can do that seamlessly (using heat and ensuring that I have a smooth splice).
Nylon is hygroscopic and can absorb clothing dye but that's more time consuming (and messy) than I want to deal with at this point. 3d printing object gallery
Inserting G-code that reverses the extruder while moving the nozzle out of the way, reverses enough to allow the old color to be removed, waits for the new color to be loaded and primed out of the nozzle, then cleanly resumes seems like the best option so far. I haven't quite worked out the best way to get the new filament loaded then wipe off any excess before resuming.