This is not my own issue yet, I heard it on [chan] bitmessage.
You can see the result image on the chan.

OS: Debian GNU/Linux 12 (bookworm) x86_64
DE: Xfce 4.18
WM: Xfwm4
WM Theme: Windowck-dark
Theme: Adwaita-dark [GTK2/3]
Icons: Windows-Eleven [GTK2/3]

White text on yellow background is almost unreadable.
It seems text color for Qt4 in the AppImage honors host GTK theme, but 'Peer's background color doesn't.
It seems to be hardcoded..

in src/bitmessagqt/networkstatus.py:

 if outbound:
 brush = QtGui.QBrush(QtGui.QColor("yellow"), QtCore.Qt.SolidPattern)
 else:
 brush = QtGui.QBrush(QtGui.QColor("green"), QtCore.Qt.SolidPattern)
 for j in range(1):
 self.tableWidgetConnectionCount.item(0, j).setBackground(brush)