Grab shader color to mix in another shader? Is it possible to grab the color of a shader, maybe by copying it's material ID or data path, and link that to a color node in another shader?

I'm working on a Cycles toon shader and I want to be able to pull in a lamp/mesh lamp color to mix with the predefined colors.

Thanks in advance for any thoughts... this is a good community.
One way is to group your colors as a node tree which can be reused in any other material: