I think the find in page is actually part of the chrome <webview> itself which would make it very difficult to change using css alone. I would doubt it to be possible using javascript either. There's info on this here: https://developer.chrome.com/apps/tags/webview#method-find And it may be possible that one of the webkit css extensions will help, but I had a look and none stand out to me: https://developer.mozilla.org/en-US/docs/Web/CSS/Webkit_Extensions

New Update with some bugfixes. Link updated.

Another possible solution - mark tabs with color https://forum.vivaldi.net/topic/16674/color-a-single-tab-or-tab-group

@dude99 I was just basing this off my (albeit non-expert) knowledge of how Vivaldi is built. I felt that compared to everything else the browser does, it wouldn't be the closest bottleneck, assuming you had animations disabled already if that was a major concern.

@Gwen-Dragon Submitted.