No label defined (Q55695)

I tried out the other filament colorizer, but got very inconsistent results due to what I think was smaller-than-designed filament size. So I designed this one specifically to fit 1.75mm filament, as well as to be much more minimal - it prints in < 20 minutes and takes very little plastic. All things considered, this works, but it has a lot of room to improve. I'd like to add some way to clip connect it to the extruder head firmly (perhaps by modifying the Mk7 filament drive block?), and I'd also like to make multiple units stackable. Finally, I have some concern that the markers aren't held all that solidly and could maybe rattle out.