To identify an invisible color in a spectral that is longer than S11 (Spectral 11) we can Normalize the color to the Visible Spectral, S11, by dividing the color's wavelength by 2 raised to the power of 11-n, where n is the color's Spectral number. To normalize an invisible color in a spectral that is shorter than the Visible Spectral, we multiply the color's wavelength by 2 raised to the power n-11. Spectral numbers start at zero (0) and increase to 21.

An example of a longer wavelength invisible color is the color at a wavelength of 588.8 micrometers in S1 :

588.8e-6 / 2^(11-1) = 575e-9 meters or 575 nanometers, making 588.8 micrometers a bright Invisible Yellow because 588.8 mm normalizes to 575 nanometers which is Yellow.

An example of a shorter wavelength invisible color is the color at a wavelength of 2 nanometers in S19 :

2e-9 X 2^(19-11) = 512e-9 meters or 512 nanometers, making 2 nanometers a nice Invisible Green because 2 nm normalizes to 512 nanometers which is Green.

A GaAlAs (Gallenium Aluminum Arsenide) Infrared Light Emitting Diode has a wavelength of 880 nanometers. What is its normallized color? It is 880e-9 / 2^(11-10) = 4.4e-7 meters or 440 nanometers, which is Blue.

Why bother?  Try mixing an Invisible Yellowish-Green at a wavelength of 325 nanometers in the Ultra Violet (S12) with an Invisible Blue at 880 nanometers in the Infrared (S10). The resulting color is in the Visible Spectral (S11) at a wavelength of 475 nanometers, a very nice Visible Light Blue bordering on Cyan.