/etc/X11/app-defaults/XGammon is in xgammon 0.99.1128-3+b2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70  | xgammon*Form.background:		DarkGoldenrod1
xgammon*Label.background:		DarkGoldenrod1
xgammon*Label.resize:			false
xgammon*Command.background:		DarkGoldenrod1
!xgammon*Command.background:		DarkGoldenrod1
xgammon*Command.resize:			false
xgammon*MenuButton.background:		DarkGoldenrod1
xgammon*text_display.background:	AntiqueWhite
xgammon*tournament_display.background:	Ivory1
xgammon*tournament_display*font:	7x14
xgammon*text_display*font:		7x14
xgammon*Label.bottom:		ChainTop
xgammon*Label.top:		ChainTop
xgammon*Label.left:		ChainLeft
xgammon*Label.right:		ChainLeft
xgammon*Command.bottom:		ChainTop
xgammon*Command.top:		ChainTop
xgammon*Command.left:		ChainLeft
xgammon*Command.right:		ChainLeft
xgammon*MenuButton.bottom:	ChainTop
xgammon*MenuButton.top:		ChainTop
xgammon*MenuButton.left:	ChainLeft
xgammon*MenuButton.right:	ChainLeft
xgammon*tournament_display.top:	ChainTop
xgammon*tournament_display.left:ChainLeft
xgammon*textdisplay.left:	ChainLeft
xgammon*tournament_display.width:	370
xgammon*tournament_display.height:	100
xgammon*text_display.width:		370
xgammon*text_display.height:		172
xgammon.x:				150
xgammon.y:				200
xgammon.boardGeometry:			390x312
xgammon.boardColor:			tan1
xgammon.darkColor:			tan3
xgammon.lightColor:			tan
xgammon.barColor:			saddlebrown
xgammon.whiteColor:			white
xgammon.blackColor:			black
xgammon*board.cursor:			dot
xgammon*board.Translations: #augment		\n\
	<Key>u:			UndoMove()      \n\
	Ctrl<Key>c:		Quit()		\n\
	Ctrl<Key>d:		Quit()		\n\
	Ctrl<Key>z:		Quit()		\n\
	<Key>q:			Quit()		\n\
	<Key>p:			PipCount()	\n\
	Ctrl<Key>f:		CompiFinish()	\n\
	Shift<Key>r:		Redraw()	\n\
	Shift<Key>S:		save(game)	\n\
	<Key>s:			save(position)	\n\
	Shift<Key>L:		load(game)	\n\
	<Key>l:			load(position)	\n\
	<Key>R:			restart()
xgammon.doublerfont:		-*-helvetica-medium-r-normal-*-12-*-*-*-*-*-*-*
xgammon.littlefont:		-*-helvetica-medium-r-normal-*-24-*-*-*-*-*-*-*
xgammon.rollout:			false
xgammon.numrollouts:			10
xgammon.watchmove:			false
xgammon.autoplay:			true
xgammon.buttonmove:			false
xgammon.stonesteps:			5
xgammon.delaytime:			5
xgammon.database:			/usr/lib/xgammon/xgammon.db
 |