We've taught our son that when the light turns red, it is time for bed. When the light is blue, it is time to get up. It has been amazingly beneficial for times

We've taught our son that when the light turns red, it is time for bed. When the light is blue, it is time to get up. It has been amazingly beneficial for times of the year like Daylight Saving ending/starting because he's not yet able to read a clock and know "Oh, its 4am - I should try and go back to sleep".