Not sure if this is being shared before, i just found it (maybe im an outdated old man...).
I run 2 screens and my secondary is mostly displaying my whatsapp/youtube/outlook and it could sometimes be glaring at night when i try to focus on some gaming or some other works on primary display.
This extensions allows you to customize most websites and they way they appear on your chrome.
try it out, whatsapp and youtube looks awesome now =D
Awesome Chrome extension