<apex:page controller="AdminController" standardStylesheets="false">

.bPageHeader .phHeader td.right {

background-color:#FF0000; } .multiforce{ color:#FF0000;

}

</apex:page>

In between make your css

for ids,classes use browser inspect element

 <apex:page controller="AdminController" standardStylesheets="false">

 <style>

.bPageHeader .phHeader td.right {

background-color:#FF0000;
}
.multiforce{
color:#FF0000;

}

</style>

 </apex:page>

In between make your css

for ids,classes use browser inspect element