Mix new colours from the filament you have with thin alternating layers

Colour mixing in recent slicers makes new colours from the filaments already loaded, by printing thin layers of each colour in turn at a ratio you set. From a distance the eye merges the layers into an in-between colour, so cyan alternating with yellow reads as green without a green spool. The trade-offs: it only looks right on vertical walls, and on a single-nozzle printer every colour swap needs a purge.

As of October 2026 the feature is in Bambu Studio from 2.5.3 (released 14 April 2026; the latest stable is now 2.8.2) and in OrcaSlicer 2.5.0 alpha (16 October 2026), which is still a test build.

This lesson builds on multi-colour printing options, which already covers filament switchers and purging.

The idea: colour from layers thinner than the eye can separate

Nothing mixes in the nozzle. The slicer orders layers by ratio: 2:1 means two layers of colour A, one of colour B, repeated. The thinner the layers, the less visible the lines. The idea came from a community fork, OrcaSlicer-FullSpectrum, which creates “virtual” filaments by alternating layers with adjustable ratios and segment heights.

In the mainline slicers:

	Bambu Studio (2.5.3 and later)	OrcaSlicer 2.5.0 alpha
Mixes	2–3 filaments	2–3 filaments of the same type
Gradients	Gradient (along height); colour curve panel from 2.7.1	gradients when Mixed color sublayer is on
Break down a target colour	Decompose Color	Decompose Color (right-click a filament)
Status	stable release	alpha, may change before stable

In OrcaSlicer a mix becomes an extra filament slot that you can paint onto the model like a real filament, and it is saved with the project. “Mixed color sublayer” sits under Process → Quality and splits layers into thinner sub-layers.

Why it only works on vertical walls

On a vertical wall you see every layer stacked tightly, so the eye blends them. On a slope each layer becomes a wide horizontal band, by the same formula as in the Z anti-aliasing lesson:

band width = layer height ÷ tan(slope angle)

At 0.08 mm layers:

1. A 70° wall (near vertical): 0.08 ÷ tan 70° ≈ 0.08 ÷ 2.75 ≈ 0.03 mm per band, invisible.
2. A 20° slope: 0.08 ÷ tan 20° ≈ 0.08 ÷ 0.364 ≈ 0.22 mm per band, bands start to show.
3. A flat top: you only see the top layer, so you get one colour, not the mix.

Several makers of test models say the same: the slope of the surface strongly affects whether colour lines show.

Design the parts you want in a mixed colour as vertical walls, and give top and bottom surfaces a real spool colour.

Working out the purge waste on a single nozzle

Multi-nozzle printers can switch heads without a full colour flush, but a single nozzle fed by several filaments has to push the old colour out at every swap. Coverage of 2.5.3 says Bambu itself recommends multi-nozzle hardware for this because single-nozzle setups waste so much.

Example: a green band 10 mm tall from cyan and yellow at 0.08 mm layers. Assume 300 mm³ purge per swap (the same figure as the multi-colour lesson; check the purging volumes table in your own slicer for the real value).

1. Layers = 10 ÷ 0.08 = 125 layers.
2. A 1:1 ratio swaps every layer = 125 swaps.
3. Purge = 125 × 300 = 37,500 mm³ = 37.5 cm³.
4. PLA weight (about 1.24 g/cm³) = 37.5 × 1.24 ≈ 46 g.
5. At 2:1 (A A B repeating) there are 2 swaps every 3 layers = 125 × 2 ÷ 3 ≈ 83 swaps → 83 × 300 = 24,900 mm³ ≈ 31 g.

Next to a part that may weigh a few grams, purge can easily be several times the part, and every swap costs time too. Check the flush/purge figure in the slicer’s statistics before you print.

The ratio also gives a rough colour: 2:1 means about two-thirds of the wall height is colour A. What the eye sees also depends on how dark and how translucent each filament is; one user reported translucent filaments worked best.

Compared with other multi-colour methods

Method	New colours	Waste	Best for
Colour change at a layer (M600)	no, spool colours only	almost none	signs, raised text
Paint after printing	any colour	none	display pieces, see sanding and painting
Colour mixing, single nozzle	yes, on vertical walls	high, scales with swaps	small parts, colour tests
Colour mixing, multi-nozzle	yes, on vertical walls	much lower	gradients, decorative models

A first try

1. Load two filaments of the same type in clearly different colours, such as cyan and yellow.
2. Create a 1:1 mix and set a thin layer height (coverage of 2.5.3 mentions layers down to 0.08 mm).
3. Print a small vertical tab or cylinder 10–15 mm tall as a swatch.
4. Look at it from 1 metre, in the light where the part will live, and adjust the ratio step by step.
5. Write down the ratio you like next to the spool names, since a new spool’s colour may drift.

Common mistakes

• Using it on tops or slopes. You get one colour or visible bands. Use vertical walls.
• Mixing different materials. Layers bond poorly, and OrcaSlicer supports one type per mix anyway.
• Not checking purge waste first. On a single nozzle, purge can outweigh the part several times over.
• Trusting the preview colour. Prediction is still evolving; print a swatch.
• Using it on load-bearing parts. There are reports of weaker layer adhesion. Test, or keep it for decoration.
• Running an alpha for important jobs. OrcaSlicer 2.5.0 is an alpha; settings and files may change before stable.

Previous: conical slicing on a 3-axis printer

Sources

• Release 2.5.0 Alpha notes (Color mixing) — OrcaSlicer Wiki
• OrcaSlicer releases — GitHub
• BambuStudio releases (2.6–2.8 colour mixing changes) — GitHub
• OrcaSlicer-FullSpectrum (mixed colours by layer alternation) — GitHub
• Has anyone tried the new Color Mixing feature on Studio 2.5.3 yet? — Bambu Lab Community Forum