Pretty much guaranteed by the fact the pages are yellow, presumably paper acidity? When I wrote my thesis, it was supposed to be on acid-free paper and archival, but I snuck in some color printed pictures, and boy did that not work out so well. 20 years later and the pages are yellow and the colors are fading.
> the photos might not be completely color-accurate
It’s hard to imagine how the web version could be accurate at all, I wouldn’t count on it, and none of the blogs nor the book mention their methodology. Even with a lot of knowledge and care, you need to know the illumination conditions (spectra of the lights) and the camera used, and the color space it was encoded into, and your display device has to be calibrated.
The best way to reproduce the colors might be to follow Boogert’s recipes for the paint, which I think is what he documented?
That's back far enough that following the recipes is bound to be _hard_.
Chemicals and pigments and such go by different names, are produced in different processes and formulations, and some are extremely hard to get due to someone noticing that it rots your genes or whatever.
Maybe whatever pigments are used in watercolors aren't affected by this much, but I bet at least some are.
It'd should be fun to try though, for a certain kind of person.
What a strange world.
Is the world better off than if we just eyeballed it?
maybe the interesting aspect is the perseverance of the author and their systematic and thorough approach and their desire to create a complete work over all watercolor pigments?