/usr/share/games/fretsonfire/data/theme.ini is in fretsonfire-game 1.3.110.dfsg2-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | [theme]
base_color = #FFFF80
selected_color = #FFBF00
background_color = #330000
|