Change centersite background color

Hi 217blaster217. You could try this CSS in a child theme style.css file or a plugin like https://www.ads-software.com/plugins/simple-css/ or https://www.ads-software.com/plugins/custom-css-js/:

/* set content and sidebar background to red */
.main-inner, .s1, .s1 .widget, .s2, .s2 .widget, .content {
  background: #5b5943 !important;
}

Thank you so much bro, you are my lifesaver ??

And is there anyway to also change color of that place where is that small heading (on second image “technika” ) also to green ? it would be glorius ??

Replace the CSS above with this:

/* set content and sidebar background to army green */
.main-inner, .s1, .s1 .widget, .s2, .s2 .widget, .content, .page-title {
  background: #5b5943 !important;
}
.page-title {
    border-bottom: 1px solid #5b5943;
}

You are god!

Well, not really but thanks for the compliment. Glad it worked.