Change flag hover and selected

Hello,

I use Polylang and it’s pretty amazing
I customized my flags, but I’m wondering if it’s possible (in the CSS maybe ?) to have different flag colors when the language is selected or the flag on hover.

Do you know what I mean ?
Do you an idea how to do it ?

Thanks a lot : )

https://ww.wp.xz.cn/plugins/polylang/