Thank you for reaching out on the ThingWorx Developers Community.
Can you confirm the file type of the 3D rendering you are using? Additionally do you have any other 3D renderings you could test this with?
I went through the documentation for this widget and see no options for coloring preferences with respect to the model itself. This would lead me to believe there was be an issue rendering this specific file or file type.
ThingWorx Technical Support Engineer