Desaturation is an unpleasant effect brought on by extended periods of exposure to a Greyzone. Colour is lost, and fairly serious numerical penalties are applied.
Desaturation provides a "-10 colourless penalty to all attack rolls, checks and saves," along with an equally nasty reduction of spell durations "to 1d4-1 rounds". Additionally, "save DCs are reduced by 10."
Desaturation often causes failure of Listen checks, resulting in characters being unable to hear one another's speech properly. Fortunately, reading of speech bubbles is not similarly impaired.