Add this to your ~/.atom/styles.less
file:
::-webkit-scrollbar {
width: 10px;
height: 10px;
}
::-webkit-scrollbar-track {
background-color: rgba(0,0,0,.2);
}
::-webkit-scrollbar-thumb {
border-radius: 0px;
background-color: rgba(255,255,255,.15);
}
::-webkit-scrollbar-thumb:hover {
background-color: rgba(255,255,255,.3)
}