13.5 The material ID

Many materials contain an attribute used to identify the material to Iray, called the material ID. The material ID attribute contains the following parameters.
Material ID in the misc section of the Attribute Editor
Material ID
Set the following attributes to modify the material ID
Applies a random integer number as an material ID for the objects to which the material is assigned. The number is generated using the material name.
This value is used to keep the material ID color for the objects to which the material is assigned consistent during an animation. There are two ways to set the material ID color of the selected material:
Type a number to define a color or click on the color field to open the RGBA Color Chooser.
Use the RGBA Color Chooser to select a color for the RGB channels and the Alpha channel of the material ID canvas.
Due to a bug in Maya on Windows OS the color field beside Material IDSet is getting dark grey after setting the color in the RGBA Color Chooser. You need to switch the Material ID attribute once and then go back to Material IDSet to see the correct color in the color field.