"Exit" button color...
Please make the "exit" button color use the theme's "highlight" color. This will match our theme and look better.
How to make a feature request for Vivaldi
If you think your problem can be solved by a missing feature, please add a request at https://forum.vivaldi.net/category/48/features-requests in the corresponding thread for your browser version.
Thanks in advance for helping us to make Vivaldi better!