Yellow is the first color perceived by the human eye. It evokes joy and clarity. My daughter was crazy about yellow flowers when she was one year old. Her excitement was contagious.
Red is screaming for attention and action. My son used to get so excited when he saw a shiny, red fire truck. We regularly visited the fire station in his first three years.
Blue is the color of tranquility and peace which supports creativity. Nurturing the right side of the brain especially in the first six years creates balance.