this jig works with my butter slider, tech2c and prusa rework x carriages.. the pen goes in from the bottom and will stay at the should stay at the same Z when you change colors. To change colors just disable steppers and move the x to the left and change your color..

If you want to use it with negative Z values in your cam software youll need to change the travel limits after homing to -0.1 on the min Z value..

Sry no photo yet my printer is currently in CNC mode:) but this will definitley works its the same inner diameter as another jig i machined in wood(offset .3 for 3d printer tolerance) check the video for it in action.. enjoy