This page provides information about Material ID Color Render Element in V-Ray for SketchUp.
Material ID Color render element creates a mask based on the material ID Color parameter. If the Material ID toggle is disabled, the material using it will appear black in the channel.
Opacity color and textures are supported by the Material ID Color channel.
This render channel is useful in a compositing process as a color mask for different materials in the scene.
How to Set Material ID Color
Each material in a scene gets an automatic Material ID Color, but you can change it from the Asset Editor. Select a material and navigate to its parameters in the right fly-off panel. Make sure to enable the Advanced Settings mode and go to the Material ID rollout. Select the preferred ID Color.