how can I design the scroll bar for Windows on Firefox?

Question

.scroll {
  height: 100px;
  background: red;
  overflow-y: scroll;
}

.scroll::-webkit-scrollbar-track {
  -webkit-box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.3);
  background-color: #F5F5F5;
}

.scroll::-webkit-scrollbar {
  width: 6px;
  background-color: #F5F5F5;
}

.scroll::-webkit-scrollbar-thumb {
  background-color: blue;
}

<div class="scroll">
  <ul>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
  </ul>
</div>

The problem is what on firefox on windows, the scroll bar is as in the picture below.

I want to look the same as on all browsers, on my linux scroll bar is blue.

Can you help me please do cross-browser on this issue?

Thanks in advance!