Change gradient background.

themes/katiola/close-active.png

themes/katiola/close-inactive.png

themes/katiola/close-pressed.png

themes/katiola/hide-active.png

themes/katiola/hide-inactive.png

themes/katiola/hide-pressed.png

themes/katiola/maximize-active.png

themes/katiola/maximize-inactive.png

themes/katiola/maximize-pressed.png

themes/katiola/maximize-toggled-active.png

themes/katiola/maximize-toggled-inactive.png

themes/katiola/maximize-toggled-pressed.png

themes/katiola/shade-active.png

themes/katiola/shade-inactive.png

themes/katiola/shade-pressed.png

themes/katiola/shade-toggled-active.png

themes/katiola/shade-toggled-inactive.png

themes/katiola/shade-toggled-pressed.png

themes/katiola/stick-active.png

themes/katiola/stick-inactive.png