Hi,
The reason you are not seeing the changes could be because of something you are doing wrong, like the way you write the CSS, or the fact you have not enabled Theme Designer Mode.
The CSS you posted is actually wrong. It should look like this...
.block_navigation.block header {
background-color: #fff;
}
Then you can do that for each block that has it's own class selector name...
.block_settings.block header {
background-color: #abc;
}
but some blocks like HTML blocks all use the same class selector name, so in this instance you would need to add the instance id like so...
#inst93.block_html.block header {
background-color: #901;
}
and like this...
#inst1033.block_html.block header {
background-color: #890;
}
You can find the 'instance' ID in the page source code. In Moodle it is this for the settings block...
<div id="inst182232" class="block_settings block hidden" aria-labelledby="instance-182232-header" role="navigation">
So the code for this would be...
#inst182232.block_settings.block
Cheers
Mary