Very useful tool, thanks a lot.
Only note, perhaps as an add-on to the symbols, tabs can be in different, not so strong colours

Why not changing tab background color?

I think it is the only addon that can mark a tab as unread.however as previously said it would be better to make it more easy to be seen.i would suggest that the area of the symbol in the tab to be bigger or maybe the symbol to be replaced with a transparent overlaid image (lets say a transparent single color image).Good job pal.