We normally do not ship anything else than Breeze theming in most KCMs, yet in the Colors KCM we ship quite a lot of other schemes.
Namely: Honeycomb, Norway, Obsidian Coast, Oxygen, Oxygen Cold, Steel, Wonton Soup, Zion and Zion (Reversed).
Aside from not being related to Breeze, most of them are also outdated. The suggestion is to remove them, and to have the Oxygen colors provided only if the style is installed.
What's up for discussion is also if we should add some more of our own color schemes, such as Breeze Darker e.g.
[x] Upload the removed color schemes to the KDE Store
[ ] Remove the old color schemes from `plasma-desktop` - D21701
[ ] Add Oxygen and Oxygen Cold to the `oxygen` repo - D21702