I can't repro this on macOS 15.3.1 with an Apple Studio Display. What display are you using? It's likely something related to color space translation.
Edit: Repro-ed using the additional steps you mentioned below. As someone who handles external bug reports and writes them, it's so often the case that there are additional steps or a specific start state required, which both prevents reproducing the bug and narrows the affected user base.
Edit: Repro-ed using the additional steps you mentioned below. As someone who handles external bug reports and writes them, it's so often the case that there are additional steps or a specific start state required, which both prevents reproducing the bug and narrows the affected user base.