I always (and only) use named colours for debugging. For example border: 1px solid red; around some element that isn't rendering as expected.

This makes it hard to accidentally forget about a rules that just just put in temporarily. Real colours will always match some design, which will have a carefully-chosen hexcode.

They're nice in prototyping styling since it's trivial to comprehend the intent of coloration while making it clear that finalized colors haven't been settled on.