ShapeClicked event will work for you, the Shape clicked is given in "e.Shape" where "e"are the parameters of the event handler.
As for the ColorPicker/ColorSelector - they provide a SelectedColor property. But the Shapes BackGround is of type Brush, same is true for the BorderBrush and Stroke. You can bind a Color to Brush (brush is represented with a sinlge color) using a Telerik.Windows.Controls.ColorToBrushConverter but the opposite is impossible - you cannot create a Color from a Brush (which is somehow a set of different colors).
the Telerik team