color pencil set

Have we ever imagined the life without colors? Have we ever noticed what is the scientific, economic and social need of colors? So, we all agree that colors do not play any essential role on the planet without which any task would be impossible to imagine. Then why different fruits, flowers, birds, animals are full of various shades!?! Why does rainbow posses VIBGYOR colors? I know the science behind rainbow is the dispersion of light through a water droplet which results in scattering of light into various shades, but which need this theory fulfills?