I’ve been trying to take picture of color standards and have people around the world use them to talk about color. It’s hard, but you are spot on.Excellent work, Steve !
If you want to get the colors as neutral as possible, and if you know a photography enthusiast or a studio, ask them to take some pictures with a (or with some) flashlight/s. That's the only defined source of light which is half way controllable at about 5500K. A modern camera will adjust to 5500K if a flash is attached.
And then, a grey-card (photographic equipment for a a few dollars) should be photographed together with any sample. Than, any user can use this card on the picture as a reference in his photo viewer (which should allow to adjust color to the reference).
There are of course more hurdles to master before the viewer gets a neutral impression (monitor setting and quality ...), but with a controlled first step you have a good start. This is in fact something which Ineos should do, as they sell their cars via Internet ...
The other thing is that modern special effects are so angle dependent, perhaps a short video of you moving around the table to catch the different color effects? These aren’t as ‘floppy’ as some out there, but it might help.
Thanks