The sensory layer of the eye?

Answer 1

The retina contains the light receptors. Rods for light level, and cones for colour.

You can perform a simple experiment to show that the colour receptors are only in the centre of the eye.

First of all get a box of coloured crayons and without looking at them, pick one, and hold it behind your head. Make sure you don't see it yet!

Looking fixedly ahead, gradually bring the crayon round the side of your head. Notice where your hand is when you first see the motion of the crayon. Continue bring it forward, noting when you can first determine the colour of the crayon.

Try again for randomly selected colours.