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Thinking about users who complain about burning white color, especially at night, YouTube offers the latest update and dark theme option to Android users' liking.
However, this dark theme does not exactly have a black color scale as it is on Twitter.
This theme, which is not entirely black, unfortunately saves battery power on OLED and AMOLED screen phones.
For the dark theme; You'll need to activate YouTube> Profile> Settings> Dark theme.
Source: https://goo.gl/2tvePv