Save Channels in PS separately

you can save your Photoshop file included the main CMYK or RGB channels and you may export one channel separately by switching off all channels that you don't want and export the visible result to a separated file.

also you can do the same effect with any colors you want (not the main CMYK or RGB) by using the "Duotones" mode.

for converting a full color image to a duotone one please do the following.

1. Convert the image to grayscale by choosing Image > Mode > Grayscale. Only 8‑bit grayscale images can be converted to duotones.
2. Choose Image > Mode > Duotone.
3. In the Duotone Options dialog box, select Preview to preview the image.
4. For the Type option, select Monotone, Duotone, Tritone, or Quadtone.
5. Click the color box (the solid square) to open the color picker, then click the Color Libraries button and select an ink book and color from the dialog box.