Color and appetite
The hypothesis that the squirrels in the red box will eat the most nuts is proven to be correct. Squirrels are affected by color in the same manner as we are.
Choosing the right color when redecorating a home or business is very important to set the right mood and feeling for the occupants. The choice of colors can influence the mood, behavior and temperament of the occupants. Restaurants, kitchens and dining rooms should be painted red or orange instead of blue, which acts to suppress one's appetite!
This science fair project may be repeated, this time, with other animals like dogs or cats.
Repeat the science project experiment, using different colored boxes like pink, yellow, orange, black, etc.
Choosing interior color - http://www.demesne.info/Improve-Your-Home/Choosing-Interior-Color.htm
Appetizing color for the dining room - http://www.decoratorsecrets.com/dining-room-color.html
Basic safety requirements. Handle animals with care to avoid being bitten.