Assigning different textures to different colors of a base texture

Let’s start with the following texture -

What I want for the final material to look like is something like this (image rendered in Photoshop) -

To put it more simply, I want to overlay a texture onto the gray region of the base texture, and have the emissive color of the material derive from the blue star in the center. How can I do something like this? It’d be awesome if someone could point me to some tutorials.

Lerp (Linear Interpolate) will be what you’re looking for, now, generating a mask from that blue and gray texture could be a little challenging. It would be much simpler if you had a simple black and white texture file, you could then feed any color you wanted into the shape with a VectorParameter or a 3Vector and however else you wanted to manipulate it. And you could easily put another texture into the background.

The problem with the grey and blue texture is that you’d need to do some hacking with some shader math to turn it into viable black and white mask.