I was also contacted by ex KEC student Adam Pritchett, who runs www.therhumboogie.com. He pointed me in the direction of the work of Leah Wolff. Wolff's watercolour work on the subject of impossible shapes particularly interest me. It is a great example of impossible objects that have colour rather being liniear or just black and white.
Many thanks to Adam Pritchett for the information on Leah wolff.