The Colour Your Taskbar Borrows From the Wallpaper

When Windows is told to pick an accent from the desktop background, it shrinks the image down to a handful of representative colours, then keeps one that is saturated enough to be seen and dark or light enough to survive on a bar. That colour then turns up in the taskbar highlight, the focus ring, a progress bar, the selected item in a menu. macOS does none of this, but the menu bar and Dock are translucent, so a blurred strip of the top and bottom edges is on show all day whether or not it was meant to be.

The awkward part is that the sampler reads the whole frame and has no idea which part of it sits behind anything. A photograph with a quiet field and one small orange kayak can hand the system that orange, and suddenly every selected row on the machine is the kayak. Pictures with a big flat area of near-neutral colour are the opposite: what comes back is close to what the eye already sees, and nothing shifts when the wallpaper cycles to the next file.

Two habits keep it predictable. Keep the top and bottom bands of the image calm, because those are the strips that translucent bars and any auto-generated tint will draw from; and if a particular accent matters, switch off the automatic option and pick it by hand, then let the image sit behind it. A gradient handles this better than most photographs, which is less about taste than about how few colours it hands over.