Resource users Reddit found a way to activate a hidden the YouTube "night mode", when the site whose color scheme is changed from white to black.
This function works in the latest version of Google Chrome. To activate it, you need to open the Developer toolbar by pressing Ctrl + Shift + I on Windows or Option + Command + I on Mac.
In the field in the Console tab, you need to insert the text document.cookie = "VISITOR_INFO1_LIVE = fPQ4jCL6EiE" and press the keyboard Enter key.
Then you need to close the toolbar and refresh the page. After this tab "Night mode" appears in the main menu (top right).
According to the portal of The Verge , the YouTube has not yet announced a new feature. Probably, it is one of the innovations that until tested.