The Simple Gray and Simple Brown themes do not replace many of the assets used in the SFRPG ruleset, yielding a mix of gray/brown assets and blue futuristic assets. One example is the Ship Combat Tracker button, but there are others in most windows.

Windows 10, 64-bit
1440x2560 resolution monitor
FGU v4.0.10 Ultimate (2021-02-04)
5E
No extensions
Clean campaign