Prusa releases MIT-licensed ColorMix model for multi-color FDM printing

Prusa has open-sourced ColorMix, a color-mixing model integrated into PrusaSlicer and EasyPrint that lets multi-material FDM printers produce dozens of color tones by interleaving thin layers of CMYKW filaments. The approach borrows from 2D halftoning: instead of dot patterns, the printer alternates colored layers thin enough that the human eye blends them at normal viewing distance. Adding a true black filament alongside cyan, magenta, yellow, and white solves the long-standing problem of CMYW-only systems producing muddy blue-grey instead of black.

The project builds directly on community work, particularly Ratdoux’s OrcaSlicer-FullSpectrum fork and Justin Rahb’s filament-mixer, which used a Mixbox-trained polynomial model originally calibrated for oil paint. Prusa’s contribution is calibrating the prediction model against actual measured FDM prints rather than borrowed pigment data, and wiring it to real material specs through the OpenPrintTag database. A dedicated Prusament CMYKW filament bundle is in production to standardize results.

Released under MIT, the model is positioned as a contribution back to the ecosystem that seeded the idea. The stated UX goal is to make multicolor printing feel like painting — load spools, see a palette, pick colors — rather than the current workflow of manually configuring extruder mix ratios for every shade.