Similar to opacity changers, you could adjust the darkness or lightness of a marking.

For example, you get a lion with maroon coat and maroon pelage. They just have a huge purple/pink back and thats a wasted slot that has no use unless you make one of the markings 0% opacity or super low opacity at that.

With the hue/burn/dodge changer, you could make the maroon coat darker than regular maroon while still preserving the marking itself.

The changes wont pass down though, and dont show up in breeding. Lions would continue to breed as usual, with lions looking the same as they do now

The only change is that, on a customizable level, you can buy a changer that will let you toy around with the darkness of the marking so it will show up better overtop another of the same color/opacity.

two same-color markings at 100% will no longer just look like one blob, they could overlay and one be darker with the hue changer without sacrificing the opacity.

It'd be a fairly expensive item too, an oasis item probably like the opacity changer is, but worth 4 gb instead of 2. Just to make it a little less common perhaps