The best experimental setup for investigating the connection between kinetic energy and temperature would be:
Placing one drop of food coloring in a cup with 50 mL of water at 10ºC; placing one drop of food coloring in a second cup with 50 mL of water at 40ºC.
This setup allows you to compare the diffusion of the food coloring in water at two different temperatures (10ºC and 40ºC), which directly correlates to kinetic energy. As temperature increases, the kinetic energy of the water molecules increases, which affects how quickly the food coloring spreads in each cup.