The system uses the materials Emissionvalue to make a highlight. As you can see the Emissionis ticked in the material below.
You can set each materials emission values to 0.5 (If you aren’t using the emission value on the object)
The script turns emission on and off so no need to do anything special. You can enable this on a per object basis by clicking the ShowEmissiveHighlighton each interactive object within your scene.