Answer:
Dependent variable: The amount of food a fish eats (as it depends on the color of food ans it may increase, decrease or change with increase, decrease or change in the color of food).
Independent variable: Color of the food (as it does not depend on any other factor).
Hypothesis: There can be two hypothesis:
1) The amount of food a fish eats gets change with the change in color of food.
2) Color of food has no effects on the amount of food a fish eats.