Ok, we'll take this under consideration. At the moment you can use this CSS code, put it in Dashboard > Comments > Settings > Styling > Custom CSS Code textarea, delete all caches and do Ctrl+F5 on front-end:
#widget-comments-container ul.wpdiscuz-widgets-tab-title-list li a,
ul.wpdiscuz-widgets-tab-title-list li,
#widget-comments-container .wpdiscuz-widgets-content, #widget-comments-container > hr{
border-color: #ff0;
}
#widget-comments-container ul.wpdiscuz-widgets-tab-title-list li.tab-title-list-active-item{
border-left-color: #ff0;
border-right-color: #ff0;
}