How to Adjust STL Surface Color?
If the PDF created from an STL file appears as a pure saturated white surface without shading, try the following steps:
1. Add File or Drag & Drop the STL file into the Input Files box
2. Select the STL file row, enable the Options checkbox, select the STL interface.
3. Then go to the Interface Settings tab, and select STL from the “Preferred Interface” drop down list.
4. Near the top of the panel is a file selector (“Apply Settings to”), pull down to pick one of the STL files at a time.
5. Then near the bottom of the panel there should be an STL Interface sub-menu.
6. The color selector can be set to the color for the individual file.
7. If more than one STL is being merged, select another STL, and set color as before.
This is a special case for STL: for most other file types you can use the Visual Effects menu. This should allow you to set up distinctive part surface colors.