"... the color profiles that now seem to be an "essential" part of a book. Frankly, I look at these as wasted pages ... the likelihood that these are some artist's best guess"
But the same can be said of the text of any non-fiction book. The author is presenting his/her best guess, based on the (almost always incomplete) evidence available and even primary sources contain errors. Yes, there are "rules" which a good historian should follow in handling evidence and citing sources but nevertheless one is presenting an interpretation.
"When multiple color profiles of some famous pilots are produced in different books, it is amusing to see the differences."
And that could equally be true of all the differing accounts of the origins of the Great War that have appeared to mark the Centenary. Interpretations differ.
All we — and profile artists — need to remember is that illustrations are just that, illustrative; they are there to help the reader picture the matter/person/place/item under discussion. I would like to see profiles accompanied by a note as to sources, which bits are guesswork and how those guesses were arrived at. It's just a matter of artists acknowledging, and readers recognising the inherent limitations of the form.
If a profile was based on perfect, colour-calibrated photos from all angles, why would you need the profile at all? The only point of including one is to bridge a gap.