Changing the header background color for homepage only

Hey guys. I need your help please.

I’d like to have a different color of the header bar on my homepage and every other pages. So I already set the color to dark grey in theme optios for all the pages, but now I want to set the color on homepage to yellow.
My website is https://www.stropexa.com

I already tried reading other threads and I put this into my custom css but it doesn’t work..:

.page-id-3 #site-header {
   color: #f8f5c8;
}

I’d really appreciate some help. Thanks!