Colours of light can be added together to form a variety of colours

How the eye sees colour The eye can only detect three colours of the visible light spectrum: –Red –Blue –Green These are known as the primary colours of light These colours then combine to form all other colours

Structure of the eye

Internal structure of the eye – notice that cone cells are located only at the back of the middle (macula) of the eye Cones cells detect colour (RBG) while rod cells detect variation of shades of colour

Normal colour vision – cone cells help us see in colour

This is how a colour blind person sees “colours”

Dysfunctions of the rods cells of the eye Partial function of the cones (red)

Additive Primary Colours Magenta is a secondary colour – a mixture of red and blue Adding green creates two new secondary colours: Green + Red = Yellow Green + Blue = Cyan Adding all three primary colours recreates white light

Combining Primary Additive Colours The three secondary colours – magenta, yellow and cyan - are also complementary to the primary colour opposite to each. Red is complementary to Cyan Green is complementary to Magenta Blue is complementary to Yellow

Combining colours of light – colour equations Red + Green + Blue = White R + G + B = W Primary colours Secondary colours Red + Blue = Magenta R + B = M Red + Green = Yellow R + G = Y Green + Blue = Cyan G + B = C

Colour blindness tests Everyone Normal – 8 R/G = 3 Normal – 29 R/G = 70 Normal – 6 Deficiency - nothing Normal – 45 Deficiency - nothing Normal = nothing CB - 45