Hi @dabinder, you will be pleased to know that we have already developed a free WPF sample application that shows you exactly what you need to do to implement succesfully color change of a WPF object when receiving gaze data.
If you download “GazeAwareElements” example from our site @ https://github.com/Tobii/interaction-samples/tree/master/WpfSamples/GazeAwareElements
This should hopefully answer your query, please let us know if we can be of any further assistance.