>"Color gradients are supposed to be equally bright around the midpoint" >This is false. Nobody mandates this. That's just because their wording is imprecise.

>"Color gradients are supposed to be equally bright around the midpoint" >This is false. Nobody mandates this. That's just because their wording is imprecise. If you replace color gradient with "perceptually linear hue gradient", which I think is strongly implied, then that would be 100% correct. Hue is a color coordinate completely independent from others like lightness, in a perceptually uniform color space. But you're on point - there's no right way to do it. Not because of it's a matter of taste or something (it's not). Problem is, there's currently no perceptually uniform color models! All models are uniform in some range but fail in various scenarios; human perception is still largely unexplored. As a result, getting it "equally bright" in different viewing conditions with varying intensities is an impossible task, especially when you know nothing about viewing conditions. You have to narrow it down to "good enough in common scenarios". Models like OKLab are trying to do exactly that.