Is there an extension or a plugin that allows for marking different tabs with colors ? I want to be able to group together a bunch of tabs that are relevant under one color using Safari.
Unfortunately the range of extensions available for Safari is pretty limited, and no one has written such an extension at this point.
Also having written an extension or two for myself in the past, there is no way to access the tabs and colour them in any way, so it would not be possible.
It may be worth looking at another browser such as Google Chrome, or Firefox.