macOS 10.15.7
Illustrator 26.3.1

Selecting text or number values within ui panels in either light or dark mode, let alone any mode, should not rely on the os or allow the os to dictate textfield colors while that textfield has focus (e.g., text selection highlight color, text color, textfield background color). Instead always use just one neutral color for each regardless of the os display mode state.

Screenshots show the selected text value (1575 px) within the Transform Panel > TextField [X pos] rendering correctly in macOS light mode and INcorrectly in dark mode.