Dark scrollbar for Firefox 57. Tested on Windows 10. Requires https://gist.github.com/Sporif/db6b3440fba0b1bcf5477afacf93f875

dark-scrollbar.as.css

scrollbar, scrollbar *, scrollcorner {
	-moz-appearance: none !important;
	--scrollbar-width: 10px;
    --scrollbar-height: var(--scrollbar-width);
}

scrollbar, scrollcorner  {
    background: #282828 !important;
}
scrollbar[orient="vertical"] {
    width: var(--scrollbar-width) !important;
    min-width: var(--scrollbar-width) !important;
}
scrollbar[orient="horizontal"] {
    height: var(--scrollbar-height) !important;
    min-height: var(--scrollbar-height) !important;
}

scrollbar thumb {
	background: #646464 !important;
}
scrollbar thumb:hover,
scrollbar thumb:active {
	background: #00ACED !important;
}

scrollbar:hover scrollbarbutton {
    background-color: #444444 !important;
}
scrollbar scrollbarbutton:hover {
    background: #646464 !important;
}
scrollbar scrollbarbutton:active {
    background: #00ACED !important;
}

Love the look of this, but is there any way to make it selective in which scrollbars it affects? For example, many websites have scrollable elements within the webpage, and I'd prefer if dark-scrollbar left those how alone. Is this possible?

@elijahtlang I don't think that's possible with just css, either you style all the scrollbars on a page (including the main one) or none of them.

Doesnt work with Firefox 68 anymore.

EDIT: nvm did everything again and it works now.

Doesnt work with Firefox 68 anymore.

It's working fine for me.

@bunnyboothe What do you mean you did everything again? I'm on FF 68.0 and it's still not working for me. I just have default scrollbars right now. Please advise.

EDIT: I made this fix in the userChrome.css and it's all working now :)

@e-t-l can you explain what you have done exactly? I'm struggling with FF 68 yet. :(

EDIT: I had to add to include Sporif. But scrollbar arrows disappeared. :(

Okay it worked with sporif's userchrome.css code? I believe they have some info in the comments of that page regarding how to activate the scrollbar arrows. Personally I leave them deactivated so I don't know offhand.

@Sporif I noticed these scrollbars get larger when the webpage is zoomed in. Is there a way to disable this scaling?

@e-t-l They get larger because he is using pixel to determine the size instead of view-width.

Edit: Try this one.