I've seen a model on Printables.com (Ninja Pot by @Wilko) which didn't show the standard orange color for the whole model. This works because the 3MF file format supports colors. Afaik some slicers even support that information for multi color prints, but I'm not sure about that. There are a few solutions how to do that (a plugin for blender, another one for OpenSCAD, afaik Netfabb), but I decided to write my own. Hopefully there isn't a totally obvious solution available that I overlooked ^^

It is hosted on Github, you can access and use it through your browser.

You can "upload" (it never leaves your browser) an 3MF file and change the color of the whole model, or you can change only some parts of it.

It has three tools:

• Mesh painting tool to paint whole objects
• Triangle painting tool to paint single triangles/faces of the model
• Triangle Neighbor painting tool which allows to paint all triangles which have the same orientation/plane

After painting you can export it a 3MF file again, and upload it to Printables. You can see an example here.

I'd love to hear some feedback from you.

There is still some work to do (Performance and I'm sure the 3MF export won't work for all models), but I'm already happy how this turned out.

Screenshot of one of my models before exporting

Uploaded to Printable