the color in the flesh of the trout comes from their diet. The yellow/orange/pink color are in the group of chemicals called carotenoids (reason why your skin will turn orange if you eat too many carrots, sweet potatoes, squash, etc.)
The critters that trout eat that add the carotenoids are usually from the crustacean family (freshwater shrimp, crayfish, etc) but below that the phytoplankton/diatoms also are sources of food for the larger crustaceans and also produce the carotenoids.
I'd like to read more about scuds to see if they add coloring to the flesh of trout. I know trout eat those when present (think the high altitude pond of wbuffetJR for example) He probably knows what color the flesh on his trout are?
You can probably influence the larger crustacean content of your pond by stocking more scuds/snails/bivalves/molluscs/freshwater shrimp or crayfish but not sure you can control the types of phytoplankton in your pond.
Keep us posted!
