Custom ListBox populated with Accent colors Rectangle

Question

i want to create a custom theme and accent changer for metroUI using MahApps . When i choose some color from these colors it change the accent of window.Color window is a ListBox which have elements which are made rectangles by DataTemplate .<img alt="" src="/forums/uploadfile/5d05e0/09012016121019PM/14112083_1060382580709717_380852382_n.gif" />.