We should use the luminosity of the color to show the amplitude of that frequency.
Because humans are better at detecting Luminosity than color()
Google “This photo is black and white”
According to vision scientist Bart Anderson from the University of Sydney, the effect we’re seeing in this illusion isn’t particularly surprising.
“The colour system is what vision scientists refer to as ‘low pass’, i.e., many of the receptive fields that code colour are quite large,” Anderson told ScienceAlert.
“So the grids get ‘averaged’ with the achromatic background, which then gets attributed to that part of the image.”
In other words, our brain kind of compresses visual information when we look at things, giving us an overall impression of what’s there if we don’t take the time to examine objects closely.
So it’s better from a UX perspective.
“colorblind people rely on the luminance contrast” from Color blindness: how to design an accessible user interface | by Ivan Tuchkov | UX Collective
So we should go form pure black to pure white.
And since people associate black with nothing we should use black for silence
We should also increase contrast by using minimum Saturation possible for colors
I suggest we go with Ironbow pseudocolor scheme. As it uses the same luminosity as grayscale and uses the intuitive cold colors for low values and warm colors for high values