Simple script for assigning visible color to segments of a spectrum, according to wavelength.
The image used as a lookup table is originally from: https://commons.wikimedia.org/wiki/File:Linear_visible_spectrum.svg
The image used for the alternative spectrum as it would appear on a gray background is from: https://commons.wikimedia.org/w/index.php?curid=9022909 (Spigget - Own work, CC BY-SA 3.0, )