How to modify the CSS of the Google Hangouts extension window in Chrome (e.g. TamperMonkey) I'm trying to remove the SMS badge from the avatar icon in my Google Hangouts conversation list. I can open the Developer Tools and make the change in the DOM, but I want an automated way to do it.

I have TamperMonkey installed, and I have a CSS declaration that works (.Dkouue {display:none}), but I can't get it to apply no matter which @match declarations I try.
Try a different extension. On Chrome, using the Stylish extension did not work for me. However, Osprey amd Stylus (with the exact same code) did. (The latter two are in fact just forks of Stylish &mdash; created because of privacy concerns related to Stylish now being part of an analytics company &mdash; but somehow they work whereas the original does not.)

The code I used for the style is the same as yours:

.Dkouue {
    display: none;
}