PrusaSlicer 2.9.6 introduces ColorMix: blending colour between layers

Prusa Research released PrusaSlicer 2.9.6 on 25 June 2026, the final build of the 2.9.6 series already previewed in a beta and a release candidate. The addition that gives the release its name is ColorMix.

What is ColorMix in PrusaSlicer?#

A multicolour filament printer does not blend molten plastic: it changes filament. ColorMix works with that limitation instead of fighting it. It alternates filaments of different colours between layers so the eye perceives an intermediate colour, in the same way a dot pattern creates tones in an ink print.

Technically it relies on virtual extruders: the user defines a mixing proportion between existing extruders and the slicer takes care of distributing the layers to approximate it.

The decision that drew the most comment is not the feature itself but how it was published: the mixing model was released as a standalone module under the MIT licence, with the stated intention that the community build on top of it. In a sector where each manufacturer tends to close off its own colour format, that is a move in the opposite direction.

What else changes in this release?#

Compared with the previous release candidate, the official notes list two specific fixes:

• Toolpath moves between the purge start and end tags are no longer shown in the G-code preview, which makes the preview far more readable on multicolour prints.
• A bug was fixed where fan speed was restored using the wrong filament's value when the tool change command was preceded by whitespace.

There is also a warning in the release note itself that is worth reading if you own an INDX printer: its profiles are not bundled with the application and are distributed through the online update, from the configuration wizard.

Why does it matter beyond Prusa?#

PrusaSlicer is the root of the tree that several of today's most widely used slicers grew from, including Bambu Studio and, through it, OrcaSlicer. What appears in PrusaSlicer usually ends up, in some form, in the others. Releasing the colour mixing model under the MIT licence makes that path shorter.

For the Mexican user there is a practical detail on top of that: multicolour by filament change wastes material on every purge. Any technique that gets more tones out of the same spools has a direct effect on cost per part, and that calculation matters more when filament is bought as an import.

Before updating#

The usual recommendation still applies: export your profiles before updating and download only from the project's official release listing. If you work on multicolour projects, save your files as 3MF rather than STL: 3MF preserves object separation and material assignment, while STL only stores triangles. The full difference is in how to open and convert 3MF.