tweaked background gradient for a better contrast to the logo

data/config_window.css

@@ -1,6 +1,6 @@
 GtkEventBox {
 	background-image: linear-gradient(to bottom, 
 									  @theme_bg_color, 
-									  shade(@theme_bg_color, 1.5) 
-									  90%);
+									  shade(@theme_bg_color, 0.93)
+									  20%);
 }