The most effective 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 for a direct comparison of how temperature affects the movement of molecules (kinetic energy) in the same volume of water. The difference in temperature is likely to result in a difference in the rate of diffusion of the food coloring due to the increased kinetic energy of the water molecules at the higher temperature, providing observable evidence of the relationship.