A group of Danish entrepreneurs have developed a 3D printing extruder unit, dubbed the Diamond Hotend, that can melt three different filaments together and produce items in rainbows of colors. This essentially allows for the printing of multiple colors from a single nozzle.
Current hot ends can only use one filament at a time, meaning that 3D printers being used to print in different colors require a unique hot end for each color. This leads to a number of problems. For one, nozzles can damage each other's work if they're not exactly the same height from the work surface. Moreover, the nozzles need to be carefully calibrated and the 3D printer's software has to constantly make corrections to achieve consistent output.
By getting rid of these problems, the Diamond Hotend allows for easier and more widespread use of multicolor 3D-printed creations.