Color gradient filament is fun stuff to play with. It lets you make 3D prints that slowly fade from one color to another along the Z-axis. [David Gozzard] wanted to do some printing with this ...

It detects the filament change moment with the help of the limit switch and controls the filament advancing gears by the 3D printer.

Practical 3D printing: The importance of filament runout sensors Here's a simple feature that can save you time and money, especially for large 3D prints.