This is explained here: > Since pure hue variations in RGB comprise less values than the total number of seconds in a day, colors are further modulated each se

This is explained here: > Since pure hue variations in RGB comprise less values than the total number of seconds in a day, colors are further modulated each second to show a distintive gamut of colors for every different moment in the day. > Variations are based on phased sine functions that respond to each individual color, the fine modulation and luminosity.