How to Change Protolink Color and GoShape Color

Hi to all.

I am a New Goprogrammer.
I want to change color of link like Line , Arrow (Protolink)and Goobject like GoCylinder,GoParallelogram in runtime like a property window . When a user want to change color of link, link type , GoCylinder and GoRectangle. Also able to change Goshape like GoRectange to GoCylinder on a simple change of property window .
can Anyone provide a sample of this.
Thanks in Advance

Demo1 has a View > Properties that brings up a property window.

Changing a GoShape requires really changing the drawable object right now, although this will be easier in 3.0 with GoFigure.