You can change all colors which i3 uses to draw the window decorations.
*Syntax*:
--------------------------------------------------------------------------
-<colorclass> <border> <background> <text> <indicator> <decoration_border>
--------------------------------------------------------------------------
+--------------------------------------------------------------------
+<colorclass> <border> <background> <text> <indicator> <child_border>
+--------------------------------------------------------------------
Where colorclass can be one of:
Colors are in HTML hex format (#rrggbb), see the following example:
*Examples (default colors)*:
----------------------------------------------------------
-# class border backgr. text indicator decoration_border
+----------------------------------------------------------------------
+# class border backgr. text indicator child_border
client.focused #4c7899 #285577 #ffffff #2e9ef4 #285577
client.focused_inactive #333333 #5f676a #ffffff #484e50 #5f676a
client.unfocused #333333 #222222 #888888 #292d2e #222222
client.placeholder #000000 #0c0c0c #ffffff #000000 #0c0c0c
client.background #ffffff
----------------------------------------------------------
+----------------------------------------------------------------------
Note that for the window decorations, the color around the child window is the
-"decoration_border", and "border" color is only the two thin lines around the
+"child_border", and "border" color is only the two thin lines around the
titlebar.
The indicator color is used for indicating where a new window will be opened.