Hmmmmmmmmm.... From a high level perspective you need to know the reflectivity of your combined pigments at that wavelength. If it's the same, they will look the same.

I don't know of anything easy you can use, but would suggest trying to find reflectance curves for each pigment you have available and making combinations that subtract to the same value at 589nm, or since 589 should be basically yellow, make up some colors where Y is constant and you change the ratio of C to R and try them out?

Low pressure sodium lamps have a pretty sharp spectrum: https://en.wikipedia.org/wiki/Sodium-vapor_lamp

Looking at the color spectrum, have you just tried and colors in the green to blue to purple range? I don’t think you need a Python library for this, I think you need to experiment. There’s a lot of dependence on the reflectivity of the material you’re looking at in addition to the color you see under sunlight or even indoor light with broad spectrum.

Try blue and green and see if both look the same under the lamp.

So I'm really not sure how this works anymore but if you figure out which frequencies alias you can use https://academo.org/demos/wavelength-to-colour-relationship/ to do a conversion.

May be useful:

Different printers have CMYK primaries with different spectra, so there’s not going to be a generic solution. But in principle, CMY can only create a linear combination of three discrete frequency bands, not a continuous spectrum.

The same will be true of the appearance under monochromatic light: you can only make colors that blend the monochromatic appearance of the primaries. So if none of the three primaries has the desired effect, you can’t create the effect by mixing them.

Would it count as easy to make the colors in a photo editing tool (picking things of the same value and saturation but different hues) and then converting to the CMYK designation?

Is there an equation for this? Like y = f(x) where y is your choice of gray and x is your color. Maybe you can empirically find “f” by fitting randomly created “x” with the resulting “y”.

If “f” can be approximated and maybe there’s something special about it so that you can find the inverse. Otherwise, you could always just generate a bunch of “x*” again, feed through “f”, and see whether the output “y*” matches your chosen gray.

Here's the Wikipedia section one general colour space, with a pretty diagram of chromaticity, and the one on CMYK colour conversion. What you want is the preimage of a CMYK colour projected into the entire perceptual space.

CMYK actually sounds kind of complicated to do this with, so yeah look for a pre-made function to convert CMYK to CIE 1931 in whatever "normal" light you have. I can help you find the preimage from that once you do.

Edit: Oh wait, this was a Halloween thing. Maybe for next year?