Hi,
How can I change the colors indicated with the arrows?
Thanks
I’m not sure how they became those colors to begin with, it looks like they are using the moz-appearance value which is not the default. Are you using the default color scheme?
Yes. I’m using default color scheme - apply to Editor-Interface-Widgets. I tried to use other schemes but the tabs always remain White. In this way the tabs are illegible 
Where can I reset all settings? I tried to uninstall and install but the settings remain.
Does Help > Troubleshooting > Restart in Safe-mode solve your problem?
Great! I solved! Thank you very much!!
That’s only a test, it didn’t permanently fix anything. You’ll have to use Help > Troubleshooting > Reset Everything if you truly want to reset everything.
But note your problem is most likely cause by an addon or a non-default color scheme (Preferences > Appearance).
Ok! Thanks!