How to Set Up PrusaSlicer for Multi-Color Printing: ColorPrint

According to Prusa Research (2026), PrusaSlicer’s ColorPrint feature has three scenarios, and the one you get depends on your printer type and how extruders are assigned to your objects. A single-material printer, or an MMU2 in single-extruder mode, can only add manual color changes. A multi-material printer with one extruder assigned to all objects can add color changes and automatic tool changes. A multi-material printer with several extruders assigned can only add color changes. Knowing which scenario applies tells you which options the slicer will offer before you touch the layer slider.

What counts as multi-color printing in PrusaSlicer?

Each ColorPrint scenario defines which actions you can place on the layer slider. The table below lists them by printer type and extruder assignment.

Single-material and MMU2 single-extruder limits

A single-material printer falls under the first scenario, so ColorPrint only lets you insert manual color changes at the heights you choose. The MMU2 follows the same rule when it runs in single-extruder mode, so it does not offer automatic tool changes in that configuration. Automatic tool changes appear only in the second scenario, where a multi-material printer has one extruder assigned to every object. The third scenario keeps color changes but drops automatic tool changes, even though several extruders are in use.

Your scenario is set by the printer profile and the extruder assignments. Changing either one can move the project into a different set of options, so check the scenario again after any change to your setup.

Extruder count, assignments and filament slots

Before you can add any color change, PrusaSlicer needs to know how many extruders the printer has and which extruder prints each part of the model. Set the extruder count first, then make the extruder assignments on the model, then load the filament slots with their colors. Changing the printer profile or the extruder assignments later can make existing changes invalid, as described below.

Set the extruder count in the printer profile

The extruder count belongs to the printer profile. Select the profile that matches your hardware and set the number of extruders to match the tool heads installed.

Assign extruders to objects, volumes or modifiers

Once the count is set, you can assign an extruder at three levels: whole objects, individual volumes (the separate parts of a multi-part object), and modifiers. Each assignment decides which extruder prints that region. Settle these assignments before you place layer-based changes on the layer slider, because the slider’s entries depend on them.

Load filament slots and match colors

Each extruder corresponds to one filament slot. Load the filament you want into every slot the model uses, and set the color of each slot in PrusaSlicer so that the preview matches the spools on the printer. Check that the slot numbers in the slicer correspond to the extruders you assigned to the model.

Add manual color changes by layer

Manual color changes in PrusaSlicer are placed on specific layers, and the options you see depend on your printer setup.

Place a change on an exact layer

To add a change, follow these steps:

1. Move the layer slider to the height where the new color should begin. Use the arrow keys to step one layer at a time and confirm the height before continuing.
2. Click the orange plus icon attached to the slider.
3. Choose the action from the menu. Depending on your setup, this is a color change or an extruder change.

The change is then tied to that layer and applies from there upward in the print.

Edit an existing change

Existing actions are edited with a right-click, not by re-adding them. To edit one, first move the slider to the layer that holds the action, because the slider must sit exactly on that layer for the edit to work. Then right-click the action and change its settings. Adding a second action on the same layer is not needed when you only want to alter the first one.

How do you paint colors onto a model?

Multi-material painting is the PrusaSlicer method for assigning colors to regions of a model’s surface, rather than inserting a color change at a given height. It has been available since PrusaSlicer 2.4, according to Prusa Research (2026). The feature offers four tools: brush, smart fill, bucket fill and height range. Use the brush for freehand strokes, the fill tools for larger areas, and height range to limit the painted area to a band of heights.

The workflow is to select the object, pick a tool, and paint the regions you want in each color. Each painted region is then sliced in its assigned color, so the result depends on how the model is segmented during slicing.

Limits to check before slicing

Painted top and bottom regions grow by the solid layer counts, so a color on a thin top surface can take up more of the model than you painted. Side-wall regions can extend inward, up to the width set in the advanced options.

Because the painting only changes how the model is sliced, you must check the sliced preview to confirm where each color lands before printing.

Tune the wipe tower and sparse layers

Each color change in a multi-color print adds height to the wipe tower, the purge structure printed beside the model. Sparse-layer handling determines how much height each change adds. According to Prusa Research (2026), enabling No sparse layers under Print Settings > Multiple Extruders makes each change add only one layer to the wipe tower. Enabling that option makes each change add only one layer to the wipe tower, which keeps the tower shorter.

To keep the tower short, follow these steps:

1. Count your color changes before slicing. Every change on the layer slider adds to the tower, so with No sparse layers enabled, a model with ten changes adds ten layers to the tower.
2. Open Print Settings > Multiple Extruders. Enable No sparse layers and confirm the setting is active before you slice.
3. Check the tower in the preview. Look at its height and footprint after slicing. If the tower is taller than the model’s color zones require, reduce the number of changes rather than accepting extra height.
4. Review the tower’s position and size settings on the same page. Compare the preview against your printer’s build area before printing.

The effect of sparse layers is only visible in the preview after each change is placed, so adjust and re-slice rather than estimating the tower height from the model alone.

Fix common multi-color problems

Three problems commonly block or silently alter a multi-color print in PrusaSlicer: changes flagged as invalid, a locked layer slider, and XY size compensation that stops applying once you paint. According to Prusa Research (2026), the first two share a root cause. The color change list no longer matches the current printer and extruder setup.

Invalid changes marked with an exclamation mark

A color change becomes invalid when you switch printer profile or change extruder assignments. PrusaSlicer marks it with an exclamation mark. Invalid changes are ignored at G-code export, so the colors switch at the wrong heights or not at all. Scan the change list before slicing and correct or delete every marked entry.

Slider edits blocked by a conflict

While a conflict is unresolved, the layer slider refuses edits, so you cannot add, move, or delete changes. Clear the conflict first. Restore the printer profile or extruder assignment the change was made for, or delete the flagged action and create it again at the correct height.

XY size compensation ignored during painting

Multi-material painting cannot be combined with XY size compensation. When both are active, PrusaSlicer ignores the compensation during slicing and displays a notification. If you paint a model, set XY size compensation back to zero on that object, then confirm the notification no longer appears before slicing.

Which setup should you choose?

Your printer hardware decides which multi-color methods PrusaSlicer offers, so start with the machine you own, then pick the effect you want within those limits.

Color changes are placed on the layer slider: move it to the target layer, click the orange plus icon and pick the action. They are available in all three scenarios.

Automatic tool changes let the printer switch filament without intervention, but only in the second scenario: a multi-material printer with one extruder assigned to all objects.

When painting beats layer-based color changes

A layer-based change is tied to a height on the layer slider. Multi-material painting assigns colors to regions of the model’s surface instead.

Painting only affects the slicing result, and painted regions cannot be exported as separate parts. Painted top and bottom regions extend by the top/bottom solid layer counts, while side-wall regions extend inward up to the limit set by mmu_segmented_region_max_width under Print Settings > Multiple Extruders > Advanced.

Matching hardware to a single workflow

Choose the simplest method your hardware supports. A single-material printer is limited to manual color changes, which suit models with a few flat color transitions. Painting becomes the better option when a color boundary must follow the model’s surface rather than a horizontal height. Keep to one method per print.

Frequently asked questions

Why does PrusaSlicer show an exclamation mark next to my color change?

The exclamation mark flags a change that is no longer valid, usually after you switch printer profile or change extruder assignments. PrusaSlicer ignores these changes at G-code export, and it blocks slider edits until you resolve the conflict. Check the affected layer and remove or recreate the action to match your current setup.

Can I assign colors to a model without placing layer changes?

Yes. Multi-material painting, available since PrusaSlicer 2.4, lets you paint regions directly on the model with brush, smart fill, bucket fill and height range tools. It supports up to 16 extruders, and painted regions affect only the slicing result, so they cannot be exported as separate parts.

Why do thin details on my painted model take the wrong color?

Thin features that the printer cannot reproduce merge into a neighboring painted region and adopt its color. Enable detect thin walls to reduce this effect.

Related reading

• PrusaSlicer vs Cura for Beginners: Which Slicer to Pick
• Best Print Speed Settings for PLA on the Ender 3 V2
• Best Layer Height for Detailed Prints: 0.10–0.15 mm Guide