Preview image lacks color when setup via "Change FIlament"

If I change a model’s color using this preview bar, instead of painting a model, it doesn’t render a preview image with the color change:

image

This can be confusing when posted to MakerWorld because a multi color plate preview looks single-color.

This mildly-NSFW model/profile combo shows the issue - the preview is solid red but the actual print will have two colors.