I’m trying to change the background color of the top bar (the one with timezone, language, login). When I inspect elements, the file that need changing is /indio/web/client/styles/partials/_messageboxes.scss. Now, in my installation, there is no folder /web/client. What to do?
Don’t change core files, if you want to do theming use a custom css file. See this part of the docs for details.