Without invoking any symbolic imagery, two of this figures SCREAM as being in accordance with two busts that I recognize, immediately.
I don't know of anyone with such a characteristically long, pointed beard as ZENO OF CITIUM. This was a well known bust, and Zeno's features are strong.
The same is true of the wide nose and shaggy face of ANTISTHENES.
In another post, I suppose that the couple pointing to the bald, longe-bearded man in orange strike me as Crates of Thebes and his wife Hipparchia, so the inclusion of Zeno and Antisthenes would strongly indicate that these are Cynics and Stoics.
If I didn't know better, I'd say that stoic MARCUS AURELIUS had his arm around the shoulder of ZENO OF CITIUM, the founder of Stoicism. Perhaps it's even PYRRHO?
At the same time, I think those two characters are also also distant candidates for Lucretius and Epicurus. I'd guess Zeno and Marcus Aurelius, as an impulse.
As to "Zeno" I agree about the beard, but doesn't Raphael have the figure as largely bald, which Zeno was not?
As to the possibility of a figure being Marcus Aurelius, do we have any other examples of someone other than from pre-Christian Greece being in the fresco?
Your reference to the colors has me asking this: I guess it's inevitable that colors are re-used, but I wonder if there is any pattern to the coloring of any of the outfits? (EDIT - I see Nate anticipated and at least partly answered my question here.)
Nate (or anyone) is there any historical or other reason to portray Zeno as fat as this orange-clad figure is shown? I agree about the beard, but the bald head combined with the very large size would seem to me to need some correlation too, or else they point in a different direction.
The figure's baldness is interesting, and also severely narrows our search.
I only know of several Greek figures that are depicted as balding.
There appear to be ten bald, or balding men in the School of Athens. Three of whom are Socrates, Plato, and Diogenes, so that leaves seven unidentified bald men:
Nothing jumps out at me. I think though, that we can cross-reference the bald and balding figures, because there are significantly fewer of them, both in the painting, and in the history of philosophers, who generally seem to sport a shaggy hairstyle.
Good sleuthing to count the balding ones in the painting. We'd have to ask elli about this, but I wonder if anything can be said about whether Greek men (ancient or modern) have a more or less tendency to go bald than Romans or other Europeans(?) I am by no means expert on the racial characteristics of Greeks but I wonder if anything can be said about their relative baldness. Maybe the number of balding men in this picture is an indication of using local figures as models rather than the busts - and maybe the sculptors tended to embellish the amount of hair?
Nate what about that pronounced downward pointed nose on the orange-balding figure. Of course we have to keep in mind Don's caveat, but the nose on the bust of Zeno doesn't seem to be so pronounced in pointing downward (?)