Topbar of third-party app with wrong color

I installed, a XMPP client, from F-Droid and noticed that when previewing the app in window mode (to select which app to go to), the topbar is on another color than expected.

I reported this to the developers of that app and they said that this is not reproducible on their side, so I thought that this could be a problem with /e/, as there are some colors changed for all apps

Can someone test this?