The defaults file is usually located inside the .crossfire directory.
This file applies to the very old X11 client for crossfire,
The newer gtk clients uses the gdefaults file as configuration file.

At the top of the file one reads :

# This file is generated automatically by cfclient.
# Manually editing is allowed, however cfclient may be a bit finicky about
# some of the matching it does.  all comparissons are case sensitive.
# 'True' and 'False' are the proper cases for those two values

Xorg is case insensitive reading it's xorg.conf configuration file,
and is able to use either False / True , Off / On , and probaly also 0 / 1 values of variables.

• cacheimages: False
• command_window: 10
• font: -misc-fixed-bold-*-normal-*-18-120-100-100-c-90-iso8859-1
• foodbeep: False
• noautorepeat: False
• port: 13327
• scrollinfo: True
• scrolllines: 36
• server: localhost
• showicon: False
• sound: True
• split: False