It took me a few weeks of tinkering but everything seems to be working now ...
0) Watched Chris's basement videos
1) Upgraded my Creality CR6-SE 3D printer to Klipper
2) Familiarized myself with the Prusa slicer (was using Cura before)
3) Tested electronics on a breadboard then designed/had board built using KiCAD
4) Refactored mk4generator code to allow me to use Klipper macros (easier to tweak things)
5) Played with a bunch of Prusa settings, bought PTFE tube with 2.5mm ID (== less jams with poor tips)
6) Modified Arduino code to support a CUT command (needed due to bowden tube)
7) Added 20KG Servo to cut filament (tip-shaping was hit/miss), with 8V from a buck-convertor
All my files are available on github: https://github.com/antonioasaro/3DChameleon
One of my 1st multi-colour prints - a ukulele keychain
From the picture it looks like good work. I can't check out the Github though. Page not found error.