Color comes from light made up of different wavelengths or frequencies. Different frequencies make different colors. The range of colors that are visible to the human eye can be found on the electromagnetic spectrum within the visible spectrum range, which is from 780 nanometers (nm) to 390 nanometers. Additionally, there are light frequencies that occur on the electromagnetic spectrum that are either too high or too low for humans to see such as ultraviolet, located just past the violet portion of the visible light spectrum or infrared, located just past the red portion of the visible light spectrum. Certain insects, like honey bees, can see ultraviolet light, while snakes, on the other hand, can see infrared light.

While fine for bees and snakes, non-visible light can be harmful to humans. For example, arc welding torches emit ultraviolet light (UV), which can cause "arc eye" or "welder's flash," which damages the outermost protective layer of cells in the cornea. Symptoms include blurred vision, intense pain, a feeling of sand or grit in the eye, tearing, burning, and headache.