https://guidebookgallery.org/screenshots/amigaos10
It seems they had at least 64 colors to choose from and they went with... Orange and white on blue? They also decided icons should be able to be arbitrary sizes for some reason, a feature I haven't seen in other GUIs.
Here's workbench 2.0, which is better but still pretty unappealing.
https://theamigamuseum.com/amiga-kickstart-workbench-os/work...
Scrolling through I thought "wait, that one doesn't look too bad" and then realized I was looking at a screenshot from Windows.