The colors of the visible spectrum are red, orange, yellow, green, blue and violet. Color is a visual representation of electromagnetic radiation. Different wavelengths and frequencies are perceived as different colors.
Color is just one part of the electromagnetic spectrum. X-rays, infrared and ultraviolet light are also created by electromagnetic radiation but are invisible to the human eye. The human eye detects wavelengths ranging from approximately 390 nanometers to 780 nanometers. Longer wavelengths have low frequencies while smaller wavelengths have high frequencies. Red has the longest wavelength and violet the shortest. Wavelengths just below red are called infrared, while those above violet are called ultraviolet.
Color is both a psychological and physiological response to light waves. Light enters the eye through the pupil and strikes the retina. Cones in the retina contain color sensing cells. Light striking these cells causes a chemical reaction that results in an electrical impulse being sent to the brain. Red, green and blue wavelengths strike cones sensitive to one particular color and send different signals to the brain. Two people may identify the same color differently though the wavelength is exactly the same. This occurs because cultural trends play a factor in the identification of color.