it could be discoloration from stress. i don't know if the fox does this for sure but a lot of fish do. i believe they have scales though. has there been any problem with your water parameters?
The color changes are a hallmark of the Foxface. Mine will change color when stressed or when 'asleep'. The scratching comment bothers me more than the color changes. Any recent addition to your tank? No white (Ich)
sand particle size dots on him right?
color changes are normal. They go from their bright Yellow to a dull Brown - Grey when they sleep or are scared or stressed. Nothing to worry about there. They are also almost impervious to Ich but scratching is a sign of something wrong.
