Change CSS

Hi,

I am trying to change the background color of the posting box from #eee to all black.

I see in the source code of the page, it is set in
bpfb_interface.css, with the following rule:

.bpfb_form_container {
padding: 1em;
background-color: #eee;
}

I change the #eee to #000 and saved the file on the server.
currently the file says #000, however the page still loads with #eee.

Any ideas? the site looks terrible with that background, having it black is a must, otherwise I would have to seek an alternative plugin.

Thank you!

https://ww.wp.xz.cn/plugins/buddypress-activity-plus/