Hello Seregka,

Would you please look at what is new in the current Firefox version :

https://www.mozilla.org/en-US/firefox/63.0/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnew

It says : Firefox theme now matches the Windows 10 OS Dark and Light modes

That means that you'd have to change that setting in Windows ....

Hi Seregka, the Default theme should follow your Windows theme if you're on Windows 10, but the Dark theme should use colors set by Mozilla for all versions of Windows. Do both of them look bad on your system?

Install an update 63.0.1. Choose the dark mode in win10 and in Firefox (or any other theme). Getting the same...

In case you're interested (maybe for future reference) :

If in Windows 10 you use a custom theme, Firefox will ignore it.

If in Windows 10 you use a dark theme and want the theme in Firefox to be light :

You can create a new integer preference named :

ui.systemUsesDarkTheme on the about:config page and set its
value to 0 ('zero') - then close and restart Firefox.