Spectral colour

A spectral colour is a colour evoked in normal human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths.

    • A spectral colour is a hue evoked in normal (trichromatic) human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths.
    • Sunshine contains nearly all spectral hues.
    • Spectral hues are commonly associated with rainbows, prisms and diagrams showing the colours of the visible spectrum (red to violet). But any medium that reflects or transmits a single wavelength of light produces a spectral colour.
    • Rainbow colours include red, orange, yellow, green, blue and violet but the human eye can distinguish many thousands of other spectral colours between each of these.
    • In a continuous spectrum of wavelengths, separate hues are indistinguishable to the human eye.
    • The intensity, which is to say, the brightness of a spectral hue viewed by an observer may alter considerably depending on the situation. For example, a low-intensity orange-yellow may appear brown, and a low-intensity yellow-green may appear olive-green.
    • Spectral colours can be mimicked by RGB colour. This involves mixing coloured lights tuned to the three spectral primaries, red, green and blue. The resulting colours are not spectral colours because of the resulting mix of wavelengths.
    • Spectral colours are sometimes called spectral hues, pure hues or monochromatic hues.
    • The fact that we see the distinct bands of colour in a rainbow is an artefact of human colour vision.