RGB light pass extend your flexibility in post-production. There is a little lengthy process to compose RGB light pass with Diffuse pass.

So, here I create a Gizmo to compose them.

For that you need basic two input

        1. Diffuse Pass

        2. RGB Light Pass

Here is the connection of this Gizmo

controllers of Gizmo. Through this controller you can change the light color and intensity indivually.  

Diffuse Pass and RGB Light pass

Impact of RGB_light Gizmo