I’m creating my new website and I would like to change the background colour. Through FireFox Inspector I nailed the CSS line that manages the colour, it’s background-color: #fff;

I now have to change that #fff
to #f3f3f3
but I cannot find the right .css file. The .css files are 4:
- block-editor-style.css
- editor-style.css
- theme-help.css
- customizer-style.css

Inside those files I find several background-color: #fff;
but none manages that header background.
Any idea what .css file manages the header background?
The inspector says “inline” which indicates that the CSS is not in a separate file, but instead is inside the HTML itself, probably in a <style>
block at line 39 ( near the top ) – search the whole page source code for #masthead
and you will probably find it.
If you want to know how it is being added to the theme HTML, you will need to search the entire project codebase for a unique string – again #masthead
might bring good results.
Update:
Added grab of the source code of your website, showing line 25 where you will find the #masthead
CSS selector, as described by Inspector – it is much further to the right – but the scroll bar is hidden, as the css is formatted into long lines.
