Utility shader's object mode uses the name of the shapes to compute the color
We can also use the Object ID Color Mode to define individual id's to object's inside a group. For example, currently, all of the windows are grouped together and so render with the same id color. If we want to change the color of one of the window objects, we can repeat the above process but apply it to the first window using a different id number (id 2).
Arnold Tag parameter added to first window with 'id 2' added to User options