Nolan C (1987; play,1989) Under the Eye of the Clock. Pan.
Bower TGR & Wishart JG (1972) Stages in the development of the object concept. Cognition 1(1).
For information on obtaining software for use in enhancing contrast.
If the learner can track objects (Section 12) and you would like to improve your knowledge about his perception of colour, you might want to try this technique. Present a ball of one colour and roll it back and forth. If he follows the movement consistently, then roll it from side to side through a tunnel (or behind a screen) to emerge at the other side. If he follows the ball and then becomes disinterested, have a different coloured ball emerge. If surprise is registered, you then know he can perceive the difference between these two colours.