Change scroll panel scroller color

As mentioned above, you need to add a custom style rule the the DOM-header. 

That is done through this code: 

$("<style type='text/css'> INSIDE STYLE RULES HERE </style>").appendTo("head");

If you want to change the color of the scrollbar thumb:
.scrollarea-btn:after {background: #000 !important; /* or a color of your choice */}

If you want to change the color of the scrollbar itself:
 .scrollarea-scrollbar:before { background-color:#fff!important; /* or a color of your choice */ }

This code doubles the width of the scrollbar:
.scrollarea-scrollbar:before { left: 10px !important; width: 20px !important; border-radius: 0px !important;} .scrollarea-btn:after { left: 10px !important; width: 20px !important; border-radius: 10px !important;}