Light is useful in everyday life because it allows us to see objects, as well as color.
Light Rays bounce onto a solid (In this case, a red car). The red car absorbs blue and green, while the red light bounces off of the car into our vision.
Red/Green/Blue are primary colors, which blend together to create new colors.
A tip to remember the colors of the rainbow: ROY G. BIV (Which stands for Red, Orange, Yellow, Green, Blue, Indigo, and Violet)