Impossible Colours

They are colours that cannot be normally seen.

Opponent Processes

The opponent colours in the Opponent Processes theory cannot be seen simultaneously.

Imaginary Colours

Imaginary Colours are the colours that cannot be produced physically, but can be done so mathematically in a colour space. When defining colour spaces, since the gamut defined by three Primary Colours, they result in a colour triangle, which cannot cover all the real colours. The gamut can be increased by selecting more than three real primary colours, but since the region of real colours is not a polygon, there will always be some colours at the edge left out. These colours are included by selecting three points outside the gamut, which are imaginary colours as the primary colours. This gamut contains the so-called imaginary colours.

No object can have these colours because it requires the cells in the eyes to be stimulated one at a time, which cannot be done.

How to see them

Be smart about your Opponent Processes. To see a green greener than normal greens, you will need to find a heavily saturated red and a heavily saturated green. Stare at the red for as long as you can, and then look at the green. The red receptors will be too fatigued to do their job and will be inhibited by the green colour. So the green receptors won't have anything to counterbalance them, so you will see a greener colour.

Examples

• Disney World used this effect in their design of the EPCOT Park, making pavements a particular shade of pink to tire out the red receptors so that the park's grasses look greener than usual.

Chimerical Colours

They are imaginary colours that can be seen temporarily by looking steadily at a strong colour until some of the cone cells become fatigued, temporarily changing their colour sensitivites, and then looking at a markedly different colour.

The direct trichromatic theory cannot explain these colours, since can involve saturation signals outside the gamut imposed by the trichromatic theory. The opponent processes theory which trats intensity and chroma as seperate signals provide a biophysical explanation of these colours.

For example, staring at a saturated primary colour field and then looking at a white object results in an afterimage of the complementary colours. Exploration of the colour space outside the range of real colours by this means is major supporting evidence for the opponent process theory. Chimeral colours are not observed to reproduce simultaneously qualities of opposing colours.

Examples:

• Stygian colours: These are simultaneously dark and impossibly saturated. e.g. To see stygian blue:- staring at bright yellow causes a dark blue afterimage, then on looking at black, the blue is seen as blue against the black, also as dark as the black.
• Self-luminous colours: e.g. To see self-luminous red:- staring at green causes a red afterimage, and then when looking at white, a red is seen against the white and may seem to be brighter than the white.
• Hyperbolic colours: These are impossibly highly saturated. e.g. To see hyperbolic orange:- staring at bright cyan causes an orange afterimage, then on looking at orange, the resulting orange afterimage seen against the orange background may cause an orange purer than the purest orange colour.