Default scrollbars on a dark theme website are just the ugliest thing. This page covers all the pseudo selectors needed to style the scrollbar.
/* width */
::-webkit-scrollbar {
width: 10px;
}
/* Track */
::-webkit-scrollbar-track {
background: #f1f1f1;
}
/* Handle */
::-webkit-scrollbar-thumb {
background: #888;
}
/* Handle on hover */
::-webkit-scrollbar-thumb:hover {
background: #555;
}