I would like to add that the problem with the codedrome.com implementation is that it is relying on an approximation to convert wavelengths to RGB, it is a shame because you really just need the Colour Matching Functions (CMFs) data for the Standard Observer of interest, i.e. 2deg or 10deg (https://github.com/colour-science/colour/blob/develop/colour...) and a 3x3 matrix to convert from CIE XYZ to the RGB colourspace of interest, e.g. sRGB (https://github.com/colour-science/colour/blob/develop/colour...).