Radio waves the least energyhave the longest wavelengthshave the most energyhave the shortest wavelengths

The electromagnetic spectrum can be defined as the collection of electromagnetic radiations that exhibit difference in range  of frequencies,wavelength and photonic energy. The longer wavelength, high frequencies contributes to low energy to the radiation.

Radio waves exhibit longest wavelength, lowest frequency in the electromagnetic spectrum which are responsible for it's low energy.

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.