Byerly lost his ability to see color, and as such, the disparity between what she's seeing and what he sees doesn't strike him as odd - not until Bastien asks that question. And then he turns and frowns curiously at him, and then at Fifi.

"This is an...elvish ability?" he asks. Discussions of the Crossroads, magic, all of that, never really stuck much in his head, but he does feel like he's encountered something along these lines.