I took color theory in art school and run a thing that collects how your brain lies to you

Hmm, are you talking about a mental discipline or a technical tool?

Grab an image editor that has a color sampling feature.

GIMP is a pain to start up, so I’ll take your word for it. Anyway, thanks for explaining, and I guess *I* was the one fooled by an optical illusion, not that my weak eyes helped me here.