Really? For me, the Active tab is the same colour as the toolbar + the text is white compared to the grey text on inactive tabs.

I would really appreciate it if you would check out my dark theme for Google Searches
https://addons.vaultpit.io/en-US/firefox/addon/dark-theme-for-google-searches/
It's in constant development so if you see something that doesn't look right, please send me an email!