I have two laptops loaded with the XFCE spin. One laptop began it's life as
Fedora 2x-something, and is now running 35, and I just reloaded the second
laptop with a fresh F35 install, and fully updated it.
Both laptops show "Adwaita" as their default theme.
The panel on the first laptop is very light gray, with black text, and looks
…normal.
The panel on the 2nd laptop, the one with a new F35 load, is very dark grey
and lightly-colored text.
Both laptops claim to be using Adwaita.
Tiebreaker: I have a third laptop, also with XFCE, and also traces its
lineage to Fedora 2x. Its appearance matches the first one.
Why is a new F35 install's Adwaita theme different? It looks downright ugly.
On the other two laptops the Adwaita theme is light-colored, and is very
similar in its brightness to the High Contrast theme. There's only minor
differences, flipping between the two. But on the odd duck the Adwaita theme
is basically the negative of the other two.