sidebars and main content background colors

For main content bg:

.page-title,
.content { background-color: red; }

For sidebars, you need to modify the background images in /img/sidebar/ to a new color, as well as this CSS:

@media only screen and (min-width: 480px) and (max-width: 1200px) {
.s2-expand .s2 { background: red; }
}
@media only screen and (min-width: 480px) and (max-width: 960px) {
.s1-expand .s1 { background: red; }
}
@media only screen and (max-width: 479px) {
.sidebar { background: red; }
}

Ok, Tnx Alx! ??

Couple of images or all?

A couple should be enough, it depends a bit on what layouts you use.

I have changed s-left.png & s-right-s2.png but nothing happens. That is not enough?
here is the link:
https://176.9.121.236/~semafors/

Problem solved! It was mistake in url path of sidebar images.