I already answered your other ticket with the same question. For your convenience, I give you the answer here as well:
will not be difficult to style the RadColorPicker control so that it
looks as you expect it to. However, it will not be easy to achieve the
behavior of the dragHandle moving only from the center of a 9 pixel square space to the center of another 9 pixel square space.
Basically, you will have to implement this feature yourself - that is,
override some of the methods of the RadColorPicker and calculate the
position of the dragHanle based on the position of the mouse.
the Telerik team