Greasy Fork is available in English.
changes the theme of youtube into a Modified White to black gradient.
< Feedback op Black Youtube by Panos modified by Sonic0170
umm greasyfork is not an application, its a site that contains scripts made for greasemonkey (firefox only) and applications like it made for other browsers
https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/
installing greasyfork
how do I install greasyfork