PxrMatteID outputs matte AOVs for compositing. This requires you add a User Attribute, explained in more detail here.
Set its type and color value.
Create a Houdini buildarray node to connect to the Utility Pattern on the PxrSurface material. Then connect a PxrMatteID Pattern node to the buildarray as shown below.
In your PxrMaterialBuilder Network, add a PxrMatteID VOP. Set the color as the user attribute above.
Connect PxrMatteID's resultAOV to PxrSurface's Utility Pattern.
Choose the correct/corresponding MatteID AOV output from the RenderMan ROP node Displays Tab