Changing the color of the bar under a selected tab

To change the color of the little bar under the selected tab make a css file and add the code at the bottom. Then when you add that css file to a form the color will change from the default blue to what ever you define in the code, for this example it will change to green

.dp-tabs .ui-tabs-nav li.ui-state-default.ui-state-active {
border-bottom: 4px solid green !important;
}