Adding to this (I'm sure you are aware), that it is a bit more complex in reality. The SPD of a non emitting medium depends on the reflectivity (as function of wavelength) of the medium and the SPD of the illuminating light source. So two materials with different reflectivities would be metamers (appear the same color) with one light source but not for a second, while if they had the same reflectivity they would appear the same color for every light source.
Absolutely! Thanks for pointing this out — it’s in fact one issue with light sources that are not full-spectrum, like fluorescents and (even “white”) LEDs. They can make objects appear to be different colors!
