How to change overflow y scrollbar styles

I've whipped up some styles for you that looks pretty similar making use of ::-webkit-scrollbar and it's sibling selectors. Note this is only for Chromium browsers, as Scrollbars aren't a part of the W3C spec and thus don't have valid selectors, outside of Chrome's relatively robust pseudo-selectors.

.large-2 {
  margin-left: 30px;
  float: left;
  height: 300px;
  overflow-y: scroll;
  margin-bottom: 25px;
  width: 100px;
  background: #ccc;
}

.force-overflow {
  min-height: 450px;
}

.large-2::-webkit-scrollbar-track {
  border: 1px solid #000;
  padding: 2px 0;
  background-color: #404040;
}

.large-2::-webkit-scrollbar {
  width: 10px;
}

.large-2::-webkit-scrollbar-thumb {
  border-radius: 10px;
  box-shadow: inset 0 0 6px rgba(0,0,0,.3);
  background-color: #737272;
  border: 1px solid #000;
}

<div class="custom">
  <div id="front_videos">
    <div class="large-2">
      <div class="force-overflow"></div>
    </div>
  </div>
</div>

There is a relatively graceful JavaScript solution called NanoScroller - though I don't personally have much experience with if, if you're looking for something with more cross-browser ability.

try this:

::-webkit-scrollbar {
    width: 12px;
}

/* Track */
::-webkit-scrollbar-track {
    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3); 
    -webkit-border-radius: 10px;
    border-radius: 10px;
}

/* Handle */
::-webkit-scrollbar-thumb {
    -webkit-border-radius: 10px;
    border-radius: 10px;
    background: rgba(255,0,0,0.8); 
    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5); 
}
::-webkit-scrollbar-thumb:window-inactive {
    background: rgba(255,0,0,0.4); 
}

Try this snippet.

::-webkit-scrollbar {
width: 20px;
}

::-webkit-scrollbar-track {
box-shadow: inset 0 0 5px grey; 
border-radius: 10px;
}

::-webkit-scrollbar-thumb {
background:black; 
border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
background:rgb(54, 56, 58); 

}