I can get x,y,z color coordinates. So how would one relate to the materials response for a particular wavelength?
First of all, given the values in your question, I think you are referring to CIE tristimulus values, XYZ (upper case), and not CIE chromaticity coordinates, xyz (lower case). The values mean very little without more information. For example you need to know the illuminant, standard observer, and measurement geometry used in their computation to define the numbers. With that information (or similar information if it is a self-luminous stimulus) you could compute CIELAB coordinates that would give you some indication of the color appearance of the stimulus. However, you have asked a more complicated question. You cannot uniquely define the spectral properties (usually reflectance) of a material from its tristimulus values. This is really the fundamental definition of metamerism. There are many spectral curves that would map to the same sets of tristimulus values. You can’t go backwards in the computation. There is an exception to this when you have a limited number of colorants with whi
