Everything is gray! (Possible issue with Channels)

I’m teaching graphic design at a school that’s currently running 2015 Adobe Photoshop. One of my students has an issue where everything in her document is gray, and we can’t change the color. Under “Channels” it reads “Gray ctrl+3” but we can’t delete it. We tried hitting ctrl+2 but it won’t reset. We also closed out of the program and reset the preferences, but were still having the same issue. Help!