A lot of times, you'll see fish that are very light in color coming from muddy water. Sometimes fish can lighten up when being caught.
If you throw one into a white five gallon bucket (with water), and let is sit for a few minutes, it may color up.
Excerpt from Robert Crais' "The Monkey's Raincoat:" "She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."
