How to create color image from three filtered monochrome images

I am trying to find out how to create a color image like astrophotographers do when filtering various wavelengths with a monochrome camera and then blending them together into an RGB image. I understand that it must be some kind of layer work, but how?

Each of the (typically) three monochrome image can be colorized like this: 

Image -> Adjustments -> Channel Mixer -> zero two of the colors for each image.

After the three monochrome images are saved as respectively red, green and blue only images, the idea is to mix these three in layers into a single full color image.

Here is an example where the photographer used some other software, but since I already pay for Adobe CC Photography, I want to use that.

So, what would be a way to mix these three color images into an RGB image?