Trouble with recustomizing my Running Blue theme

[kotourist]

Hello. I've already read and made a lot, but I failed to do the thing I want.
I'm using Running Blue expressive and with help of Firebug I found, that in screen.css there is such code:
.layout-wt #content-inner {
background:url("bg-content-wt.gif") repeat-y scroll right top #FFFFFF;

My aim is to remake the colour of background of content-inner to #212121. To do this I've tried several things
1. In the Custom CSS block I've printed
#content-inner {
background:#212121;
background-color:#212121;

2.I've read the article http://community.livejournal.com/s2expressive/49888.html#cutid6
and made my layer with code

layerinfo "type" = "theme";
layerinfo "name" = "kotourist_layer";
set base_theme = "running-blue";
set theme_designer = "Tiffany Chow";
set theme_designer_type = "outside";

set custom_css = "/* MYYYYYYYYYYYYYYYYYYYYYYYYYYYY */

#content {
background:#212121;
background-color:#212121;

}

#content-inner {
width: 1210px;
background:#212121;
background-color:#212121;

}
";

It didn't help me. The background color remains white.
The question is do I have to create my own style from scratch to change the color or there is some method of changing it in existing theme "running blue" (redefine it in screen.css or define my own and put it above the existing one not to rewrite all other parameters)?

Thank you for help