In 1671, Sir Issac Newton postulated that all color was inherent in white light, but different materials reflect different colors in the white light. He proved that color is an object interacting with already colored light rather than objects themselves creating the color. A great proof of this is the prism, which takes white light & disperses it so that each wavelength of electromagnetic radiation (light) leaves the prism at a slightly different angle, illustrating the visible spectrum…
All matter has a resonant frequency that is represented in this table by their spectral emission when observed via Spectroscopy. As you can imagine, some of these frequencies fall within the visible light spectrum. http://www.fieldtestedsystems.com/ A Microwaved Planet's photo. PeriodicTableSpectra http://www.fieldtestedsystems.com/
A typical human eye sees wavelengths from about 380 to 750nm. The visible spectrum starts with violet at 350nm, then indigo, blue, green, yellow, orange, & finally red. A rainbow is a continuous spectrum of the colors of the visible spectrum. A great way to remember what colors are in the rainbow (visible spectrum) is by making the acquaintance of Mr Roy G. Biv. A mnemonic for the sequence of colors in the visible spectrum, in rainbows, & in order from longest to shortest wavelength.
Electromagnetic spectrum: radio, TV transmission, visible light, infrared, ultraviolet radiation, x rays, gamma rays; despite vast differences in uses & means of production, these are all electromagnetic waves w/ same general characteristics, including propagation speed (in vacuum) of c & the relation c = wavelength times frequency holds for each