I am constantly swapping which filament is going into my mmu2s and I often have to follow the tube back to the unit to figure out which input it is. With a simple filament number it is now very easy for me to identify which tube belongs to which input, it is now easy for me to swap and change things around. Hooray! 

Update - I have included a .stl for numbers 1 - 9 for people that require more.