3D Print Colorizer is a combination of 3D printed parts and a Cura plugin which allows anyone with an Ender 3 like 3D printer to produce multi colored models. Have a look at some results:
How it works
3D Print Colorizer uses Sharpie or Sharpie-like permanent markers to directly paint on the layers of a 3D print. After a layer is finished printing normally a pen holder, which is mounted to the print head, is used to fetch pens from a special pen rack mounted to the top part of the printer. Normal printing and painting is used alternately to produce a final colored model.
To coordinate the process a special Cura plugin is used to add the painting G-Code. After installing the plugin you need to enter some calibration values and afterwards models sliced for an Multi Extrusion printer can be printed on an Ender 3 with full color support.
Detailed installation instruction are given in the Wiki. Please follow each step to complete the installation and get ready for mutli color printing.