STL: geometry only
An STL describes shape but not colour. For a single-colour sign it gives you one file that every slicer understands. For multicolour it is not enough on its own because there is nowhere to record which part uses each colour.
3MF: colour built in
A 3MF stores each part with its own material, so your slicer opens the sign already split by colour. This is the best choice for multi-material printers such as those with an AMS: load your filaments, confirm the assignments and print. Coloured 3MF export is a Pro feature.
Split-STL pack: for manual swaps
No AMS? Pro can export a split-STL pack: a zip with one clean STL per colour, all sharing the same origin. Import them together, assign a colour to each, and use the colour-change workflow supported by your printer and slicer.
Whichever you choose, the parts share a common origin, so the colours stay aligned.
Quick rule of thumb
- One colour → STL.
- Multicolour on an AMS / multi-material printer → 3MF.
- Multicolour with manual filament changes → split-STL pack.