The Great Yellow Signal Light Debate

In the back seat of Mrs. Scott's car, after coming to a light, our two oldest had an argument over the meaning of a yellow signal light.

Seven year old: "It's a warning that the light will turn red."
Four year old: "It means that the light will turn red and to slow down."
7: "You don't have to slow down. It's just going to turn red."
4: "You're supposed to slow down. When the light turns yellow, mommy slows down and stops."
7: "When the light turns yellow, daddy goes through it."