Can I use object's Custom Properties inside Cycles materials? I wonder if maybe the Attribute node in Cycles can bring in a Custom Property of an object.

I have a model that has an LED light, and I wish I could change the color of the LED on different instances of the model, without using different materials.
An alternative to using the pass ID is using the object name and an OSL script. It is not very elegant either, but at least allows for setting multiple values. I have explained it here.