Blender workflow for color printing

Create object in Blender:

Do your generic 3D print prep work
UV-Unwrap the object.
- It's best to use a manual unwrapping method (mark edges) as the smart UV unwrap leaves visible marks on the texture. (Although this might be solved when increasing the gap between islands)
- Make sure to have large gaps between islands (can a safe minimum be calculated?)
- Problem with visible seams in 3DPrint: is it because it's texture downsampling option?
Open the texture and lay out the UV (or use Cycles to bake the 3D view to the texture)
- A texture of 2048x2048px should work fine for medium sized objects. Alpha enabled, 32 bit float unchecked.
Save as a PNG file, so it's external to the project.
connect your texture to the Principaled BSDF shader, and the shader to the material surface output. This might look bad, but otherwise the texture is not linked in the exported .mtl file.
- https://blender.stackexchange.com/questions/149081/mtl-file-after-exporting-comes-without-texture-map-map-kd
Export as OBJ & set Path type: copy (blender copies texture file to destination folder)

Open the OBJ file (the texture file will be automatically loaded)
Optionally make hollow, put in holes and perform pre-print checks
Export 3D model as VRML (.wrl) file. (The texture file will be exported as well)

Open the exported .wrl file and check if the texture is present.
Place on the build platform (the back end is more stable)
Click 'Tools > Build Time Estimator' (button) to get info for the part cost excel file.
Start printing

Notes

The textures in 3DSprint might appear extremely low resolution. The VRML file however is exported in full resolution.
- This is a render setting (purely visual). Go to settings to change to high quality texture rendering.
Blender: speckles on bake are caused by overlapping mesh geometry. Remesh and they should go away.
3DPrint: visible seams: avoid using a large texture file. Keep it 2x2K. Allow more space between islands.
- experiment with alpha or non-alpha