Block background color

You will need to find the CSS #id of the block (use firebug in firefox) and then add the following code to the theme CSS (structure.css should do).

#block-id .block-title {
   background:#111;
   color:#FFF;
   padding:5px 10px;
   margin:0;
}

#block-id .content {
    background:#fff;
    color:#111;
}

A follow-up question (kinda) ... is there a way to make the title background of a specific block a different color to the title background of all other blocks? I am trying to give visual prominence to a particular block and just making its text a different color, though easy, is not what I want. Thanks for any help.

It should work the same way posted above :

#id-of-your-block .block-title {
   background:#111;
}

where can i get the css #id of my block?
and where do i have to paste the given code in order to give the background???