Colors are the result of the selective reflection and absorption of white light. Colors comprise all the wavelengths of white light visible to the human eye.
Humans perceive color because of the way in which different materials interact with light. Objects do no possess color, they simply reflect certain wavelengths of light that appear as color to the human eye. The electrons of all atoms vibrate at specific frequencies. When atoms interact with a wavelength of light of the same frequency as their electrons' vibration, they absorb that light. If the wavelength differs in frequency from the electrons, it reflects and appears as color to the eye.
The spectrum of visible light consists of wavelengths from approximately 380 nanometers to 780 nanometers. At the lowest end of the visible spectrum humans perceive the color violet. The highest end of the spectrum is red. White light breaks down into the visible spectrum upon exposure to a prism, such as water or glass. This property of white light is responsible for the appearance of rainbows on wet, sunny days.
When atoms absorb a wavelength of light, rather than reflecting it, the energy of the light becomes motion. This motion then becomes thermal, or heat, energy. This is why dark or black surfaces, which absorb all wavelengths of white light, become warmer than other-colored surfaces on a sunny day.