You cannot permanently shut off any of RGB color channels. However, it is possible to use the RGB color channels to get the affect you want.

1. Hide the Red red and Green green color channels
2. Select the blue color channel
3. Edit the Blue blue color channel making it completely black
4. Show the Red ged and Green green color channels
5. Save As...

Check out this link for and explanation of why this works.

You cannot permanently shut off any of RGB color channels. However, it is possible to use the RGB color channels to get the affect you want.

1. Hide the Red and Green color channels
2. Edit the Blue color channel making it completely black
3. Show the Red and Green color channels
4. Save As...

Check out this link for and explanation of why this works.