Multi-Colour 3D Printing on a Single Extruder: Everything You Need to Know

Single-extruder multi-colour printing works through three main approaches: filament swaps at a specific layer (simplest — two distinct colour zones), colour-change during a pause mid-print (manual but effective), and manual filament blending or gradient spools (complex but visually striking). None of these produce the per-layer, per-area colour control of a true multi-material unit — but for most two-tone prints, layer-based swapping is quick, easy, and the results are clean.

How does single-extruder multi-colour printing work?

A single-extruder FDM printer can only have one filament loaded at a time. Multi-colour printing on a single extruder therefore works by pausing the print, manually swapping the filament, and resuming — with the new colour continuing from where the previous one left off. The result is a print where different sections are different colours, divided at horizontal layer boundaries.

This is fundamentally different from multi-material systems (like the ELEGOO Roto or Bambu Lab AMS), which can switch colours within the same layer. Single-extruder colour changes are always at layer boundaries, which means the colour zones are always horizontal bands — not areas within a single layer. Understanding this constraint tells you immediately what kinds of prints this technique suits and which it doesn't.

Method 1: M600 filament change command (recommended for most users)

The most reliable approach is to add a M600 command directly into the G-code at the layer where you want the colour change. M600 is a standard Marlin firmware command that tells the printer to park the nozzle, unload the filament, beep, and wait for you to load new filament before resuming.

Setting it up in Cura

1. Slice your print normally and export the G-code. Open the file in a text editor (VS Code, Notepad++).
2. Find the layer where you want the colour change. G-code layers are preceded by a comment like ;LAYER:n. Use Ctrl+F to find the specific layer number.
3. On the line immediately before that layer's first movement command, insert: M600
4. Save the file and print it. The printer will pause at that layer and wait for you to swap filament and confirm the resume.

During the swap: the purge matters

When you load the new colour, the old colour will still be in the hot end, mixing zone, and nozzle. You need to purge enough of the new filament to clear all the old colour before resuming, or you'll get a colour bleed zone at the change point. The M600 command in most Marlin configurations prompts you to purge — manually extrude 30–50mm of the new filament into a wipe bucket or manually until the colour appears clean, then confirm the resume.

Darker to lighter colour changes require more purging than lighter to darker.

Method 2: Pause at Z-height (manual approach)

Most modern printers with a display panel allow you to manually pause a print at any point and resume. The sequence is: watch the print progress, pause via the printer's menu when the nozzle reaches the colour change layer, swap filament manually through the Change Filament menu, purge, and resume. This requires you to watch the print, but no G-code editing is needed.

It's less precise than an M600 command — you may miss the exact layer if you're not watching closely — but works well for casual use and for testing the technique before committing to G-code modification.

Method 3: Gradient and silk rainbow filaments

Some filament spools are manufactured with a colour gradient built in — the filament gradually transitions through multiple colours along the length of the spool. Silk rainbow PLA is a popular example, and it produces visually striking multicolour prints with zero configuration changes. The colour pattern depends entirely on where you start printing on the spool and the size of your print — you can't control exactly which colour lands where.

This is the easiest approach for decorative prints where the specific colour placement doesn't matter — vases, sculptures, display pieces. Toner and Ink stocks silk and rainbow PLA from ELEGOO and local suppliers.

What single-extruder colour changing can't do

It's worth being clear about the limitation: single-extruder colour changes can only change colour at horizontal layer boundaries. Within any single layer, the entire layer is one colour. You cannot, for example, print a white letter on a black background within the same layer — that requires a dedicated multi-material system.

Prints that work perfectly with single-extruder colour change

Despite the layer boundary constraint, there are many prints where single-extruder colour changing produces excellent results:

• Signs and nameplates — the base in one colour, the raised text in another
• Lithophanes — many lithophane models are designed with a solid colour change at a specific height
• Decorative vases and bowls — horizontal colour bands are visually effective on cylindrical forms
• Tiered display bases — different tier heights in different colours
• Miniature terrain — brown base layer, grey rock sections, green top — works well as distinct horizontal zones