Hello!
You can start with the following example:
<%@ Page Language="C#" %>
<%@ Register assembly="Ext.Net" namespace="Ext.Net" tagprefix="ext" %>
<!DOCTYPE html>
<html>
<head runat="server">
<title>Ext.NET Examples</title>
<style>
.x-form-empty-field {
color: brown;
}
.x-form-focus {
color: brown;
}
.x-boundlist-item {
color: gray;
}
.x-boundlist-item-over {
color: #FFF;
background: none repeat scroll 0 0 brown;
}
.x-form-trigger {
/*background: url('url_to_your_sprite_for_trigger');*/
}
</style>
</head>
<body>
<ext:ResourceManager runat="server" />
<ext:ComboBox runat="server" EmptyText="Pick a Month">
<Items>
<ext:ListItem Text="January" />
<ext:ListItem Text="February" />
<ext:ListItem Text="March" />
<ext:ListItem Text="April" />
<ext:ListItem Text="May" />
<ext:ListItem Text="June" />
<ext:ListItem Text="July" />
</Items>
</ext:ComboBox>
</body>
</html>
However, you have to prepare your own sprite images for triggers and customize scrollbars. I think this article will be helpful:
http://webdesign.tutsplus.com/tutori...our-ui-design/