Why my system theme is light ? My settings is :
https://ibb.co/C631yt1
Hi @bogdan546! Your Firefox theme is light because your operating system (like macOS, Windows, Linux) is set to light.
You can change your Firefox theme at any time. 
Here are instructions for how to do so: https://support.mozilla.org/kb/use-themes-change-look-of-firefox
But the same theme were is set before 89 and firefox toolbar were blue and now is grey light. This is my windows theme
https://ibb.co/10PyRDF
Based on those screenshots, I’m not sure what happened. 
Have you tried selecting Windows Light and seeing if that changes Firefox back t the way it looked before?
I tried, but it didn’t work