Nice demo from Sebastiano Guerriero. When a fixed-position header moves from overlapping differently-colored backgrounds, the colors flop out to be appropriate for that background. Sebastiano’s technique is very clever, involving multiple copies of the header within each section (where the copies are hidden from screenreaders) which are all positioned on top of each other and then revealed as the new section comes, thanks to each section having a clip-path around it.
A bonafide CSS trick if I’ve ever seen one.
It makes me wish there was an easier way of doing it. Like, what if there was some magical value of mix-blend-mode that would handle it? I got close enough that it gives me hope.