ext-theme-classic-all.css
x-window-header-default-collapsed-top{-webkit-border-radius:5px;-moz-border-radius:5px;-ms-border-radius:5px;-o-border-radius:5px;border-radius:5px;padding:4px 5px 4px 5px;border-width:1px;border-style:solid;background-color:#ced9e7}

por

x-window-header-default-collapsed-top{-webkit-border-radius:5px;-moz-border-radius:5px;-ms-border-radius:5px;-o-border-radius:5px;border-radius:5px;padding:4px 5px 4px 5px;border-width:1px;border-style:solid;background-color:#17ff03}