OK, interesting: iOS 18 beta 3 seems to be doing an intelligent auto-dark tint on some third party app icons. It’s reliably triggered by being a clearly delineated shape on a white background. Other icons just get a slight ‘darkening’ effect applied.

BUT! check out that Facebook icon invert. Some kind of computational icon design happening here. Wild.

@sdw Looks like same logic on Facebook icon as Mail icon
@danielkasaj @sdw Logic seems to be White/Colour to Colour/Black. Even though the Colour is a gradient instead – other ones that might seem as gradients really aren't.