What Wavelength Goes With a Color?
This page is from http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html
Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled "visible light". This "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light. Earth's most important energy source is the Sun. Sunlight consists of the entire electromagnetic spectrum.
(Wavelength image from Universe by Freedman and Kaufmann.)

Violet Light The visible violet light has a wavelength of about 400 nm. Within the visible wavelength spectrum, violet and blue wavelengths are scattered more efficiently than other wavelengths. The sky looks blue, not violet, because our eyes are more sensitive to blue light (the sun also emits more energy as blue light than as violet).
Indigo Light The visible indigo light has a wavelength of about 445 nm.
Blue Light The visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere. This causes the sky to appear blue.
Green Light The visible green light has a wavelength of about 510 nm. Grass, for example, appears green because all of the colors in the visible part of the spectrum are absorbed into the leaves of the grass except green. Green is reflected, therefore grass appears green.
Yellow Light The visible yellow light has a wavelength of about 570 nm. Low-pressure sodium lamps, like those used in some parking lots, emit a yellow (wavelength 589 nm) light.
Orange Light The visible orange light has a wavelength of about 590 nm.
Red Light The visible red light has a wavelength of about 650 nm. At sunrise and sunset, red or orange colors are present because the wavelengths associated with these colors are less efficiently scattered by the atmosphere than the shorter wavelength colors (e.g., blue and purple). A large amount of blue and violet light has been removed as a result of scattering and the longwave colors, such as red and orange, are more readily seen.