Multicolor D&D Miniatures on Bambu AMS from a Single-Color STL

Most miniature STLs come as one solid mesh with no color information. That's fine if you plan to prime it and paint it with a brush. But if you have an AMS on the printer, you can print the base colors in filament instead of printing a grey wizard and spending an evening on basecoats.

This guide takes a plain single-color STL to a multicolour print on a Bambu AMS. Most of it applies to any painter, but the steps use Layerpaint, which I build for exactly this job.

What you need

A Bambu printer with an AMS-family unit. One AMS unit gives you 4 filament slots. Bambu's P1 guide documents chaining up to four units for 16 slots (Bambu Lab Wiki: P1 multi-color printing). Most people painting minis have one unit, so this guide plans for 4 colors.
A single-color STL, OBJ or 3MF of the mini. Layerpaint loads all three.
Bambu Studio to slice and send the job.
A desktop browser: Chrome, Edge, Firefox or Safari. You don't need an account to paint.

Step 1: Pick your four colors before you paint

This is where most mini color schemes go wrong. You have four slots, so the whole model gets four colors, base included. A D&D fighter might use:

Skin tone
Armour (silver or grey)
Cloth or tunic color
Base and leather (one dark brown can do both)

Pick spools you actually own. Layerpaint's color picker has 600+ real filament colors by brand (Bambu, Polymaker, Prusament, Overture and others), plus theme palettes (Warhammer, fantasy, sci-fi) and skin tones. Add them to the palette in the order they sit in your AMS: slot 1 first, then slot 2, and so on. That keeps the mapping simple later.

Step 2: Load the STL in the browser

Open the painter and drag your STL onto the page. Painting by hand runs entirely in your browser, so the file isn't uploaded anywhere. That matters if you're working on a paid or Patreon sculpt you aren't allowed to share.

Step 3: Block in the big areas with Magic Fill

Don't start with a brush. Layerpaint reads the model's hard edges and splits it into regions by crease angle. Magic Fill floods out from one click until it reaches those creases, so a cloak, a shield face or a pauldron is one click.

Click a surface to preview the fill, scroll to adjust it one degree at a time, then click again to apply the color.
Turn on Symmetry for armour and symmetrical poses, so every stroke is mirrored across an axis.
Use Isolate & Cut to hide whatever is in the way, like an arm across the chest, or drop a guard sheet the paint tools won't cross.

Step 4: Detail with the brush, then clean up

Faces, belts, gems and eyes are the hard part. Switch to the Brush; fine mode follows the plane you click and respects borders you've drawn. If two colors need a clean split where there's no crease, draw a Border first, then fill each side.

Then tidy up:

Clean up stray specks and fill bare gaps.
Watch the too-thin-to-print flags. A patch narrower than the slicer's outer wall won't survive slicing.

A color edge can only be as sharp as the triangles it follows. A low-poly STL gives blocky edges whatever tool you use.

Step 5: Check filament swaps before you slice

Every color change on a layer is a filament swap, and swaps cost purge waste and time. Layerpaint's Print check lets you scrub the model layer by layer with a per-layer swap counter. If one stray fleck of skin color adds a swap to dozens of layers, you'll see it here and can fix it before slicing. See also cutting AMS purge waste with palette order.

Step 6: Export a Standard 3MF

Export saves a Standard 3MF using the official 3MF Materials Extension. Your first hand-painted export is free. After that, it's 10 exports for $6.97 or $39.97 once for unlimited. No subscription.

Save a .layerpaint project too, so you can come back and change colors later.

Step 7: Open in Bambu Studio and map to your AMS

Open the 3MF in Bambu Studio. The colors come in already painted, so there's nothing to repaint in the slicer. When you send the job, Bambu Studio builds the AMS mapping by matching filament type and color, and you can change it if it picks the wrong slot (Bambu Lab Wiki: Multi-Color Printing; Use AMS on Bambu Studio). Picking your real spools in Step 1 is what makes that automatic match land.

Then slice as normal. On a multicolour mini, a good share of the filament goes into the prime tower and purge, so it's worth checking those before you print.

Common problems

The mini printed in one color. Usually the colors didn't come through on import, or every color mapped to the same AMS slot. Check the mapping when you send the job, and see multicolour print came out one color after slicing.

Too many swaps or a big purge pile. Cut colors that appear on lots of layers, and use the swap counter to find stray specks.

Blocky color edges. The mesh is low-poly at that spot. Use a higher-resolution STL if the designer offers one.

What filament can't do. Filament color is flat and opaque: no washes, highlights or real metallics. It replaces the basecoat, not the brushwork. See how to paint miniatures faster by printing the base colors.

FAQ

How many colors can a mini have? As many as you have slots loaded: 4 per AMS unit. For more colors than slots, see painting with more colors than AMS slots.

Is my sculpt uploaded? No. Hand painting runs in your browser.

Does it work with OrcaSlicer or PrusaSlicer? Yes. The same 3MF opens colored in OrcaSlicer and PrusaSlicer.

Try it on your next mini

Take the single-color STL you were going to prime anyway, drop it into Layerpaint, and paint it in your four AMS colors. No account, nothing uploaded, and your first hand-painted export is free.