Customizations for www.youtube.com via StyleURL.

style103.css

body {
    --yt-app-background: rgba(0,0,0,0.7);
    --yt-main-app-background: rgba(0,0,0,0.7);
    --yt-main-app-background-tmp: rgba(0, 0, 0, 0.22);
    --yt-primary-text-color: white;
    --yt-spec-text-primary: white;
    --yt-endpoint-visited-color: white;
    --ytd-video-publish-date-color: white;
    --yt-metadata-color: #ffffffb5;
    --yt-button-color: white;
    --yt-icon-color: white;
    --ytd-comment-text-color: #ffffffad;
    --yt-button-text-color: #ffffffad;
    --yt-placeholder-text-color: #ffffff59;
}

Stylefile.yml

---
version: 1.0
domains:
- www.youtube.com
url_patterns:
- www.youtube.com/*
timestamp: '2018-08-02T20:46:51Z'
id: pqTX
redirect_url: https://www.youtube.com/watch?v=s0vg_H9hBuU
shared_via: StyleURL - (https://styleurl.app) import and export CSS changes from Chrome
  Inspector to a Gist you can share (like this one!).