I didn’t mention this earlier, but a while ago, I noticed the wavelength node in Blender didn’t seem to give the correct colors (while also exploring a way to render spectral colors). I was able to find some functions that were fit to the CIE 1931 color matching functions in this article: Click!
It’s implemented in this Blender file: Click!
It should be using the sRGB D65 color space with a D65 illuminant.