It's just like when you mix paints of all different colors and end up with brown. Mix foods of all different colors and they end up brown...
Have him eat a lot of watermelon some time and see if it changes! I think beets will also make changes.
He sounds like my kind of kid! My son, after watching cows mate, wanted to know how snakes do it.
You make your choices, and you live with them. In the end, you are those choices.
"Strength is the mental and physical fortitude to endure, resilience to bounce back, and force to create change, allowing you to thrive in any circumstance and through any adversity." TrPAssassin