hi
to change the theme color via CSS files, which is the file i should go in to change :-

Style ie-Css
Style Css
tabs.Css
or others

can you please give the line number to change the header green on top, beside "search in" main page
thank you

@thevarajah22
You should change style.css only.
In some cases when you need to modify view on mobile, responsive styles are in responsive.css

Nothing else required.