Id Color Pass is a node-based method from Luiz Kowalski for generating a coloured ID pass inside Blender. It centres on an id_pass NodeTree that you append into your own file, then assign an ID to each object or material.
The workflow runs through Blender's compositor. You enable IndexOB or IndexMA in the Render Layers Properties, switch on Composition Nodes, and connect the id_pass group after the IndexOB or IndexMA output on the Render Layers node. The result is a coloured ID pass.
It targets Blender 2.79 and is released under the GPL license, with documentation included. The listing records 80+ sales on Superhive, and it's shown here as free. Check the developer's page for current licensing and any compatibility notes beyond the listed version.