For Tom's sample

by wales

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/extjs/3.4.1-1/adapter/ext/ext-base.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/extjs/3.4.1-1/ext-all.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/extjs/3.4.1-1/resources/css/ext-all.css">
<body>
    <div id="container">
    
    </div>
</body>

CSS

.test .x-panel-header-text{
    color:blue;
}

.test .x-panel-header{
    background-color:white;
    background-image:url();
}

JavaScript

Ext.onReady(function(){
    new Ext.Panel({
        title: '白底藍字的panel by class test',
        renderTo: 'container',
        width:500,
        height:300,
        layout:'fit',
        cls:"test",
        items: {
            xtype: 'label',
            text:'紅色的字by style',
            style:{
            	"color": "red"
        	}
        }
    });
});