As you said our gauges (since Q3 2011 and included in the DataVisualization assembly
) have simple and quite flat default themes. Our idea was to introduce simple structure which can be easily customized.
Changing the main colors of a gauge can be easily done by using the exposed OuterBackground
properties. However if you need the exact look from the screenshot (especially the geometry), then it will be best to create a Custom Template.
Let me know how this works for you and whether you need further assistance.
the Telerik team