Because one is controlled and the other is not. If the color is indeed the one set by the dev/designer/... and it's juste not the right one, that's a controlle

Because one is controlled and the other is not. If the color is indeed the one set by the dev/designer/... and it's juste not the right one, that's a controlled thing, it's not severe. The app is doing what you want it to, you just gave it the wrong instructions. The crash on the other hand is uncontrolled. That's severe, because it's a case where the app is not doing what you want it to. Severity is something for the dev team internally, priority is something for the product manager and business people that the dev team follows. When you start mixing the two in a single thing, the dev specific needs are always what goes out the window first.