Colour Theory: Perception and Optical Effects

Quick overview of colour in design

Design Questions

  • What design elements are perceived first and why?
  • Why are some colours seen more easily than others?
  • Which colour combinations create harmony? Which colour combinations shock?
  • Why do colour illusions occur?
  • How can we use all these factors to enhance communication in designs?

The Eye

As light passes into the eye it comes into contact with the retina. The retina is made up of layers of different cells, including those known as rods (100 million) and cones (6 million)

Rod cells are better for low-light vision and enable us to see dimly lit forms but can only sense the intensity of light.

Cone cells can also discern colour, they function best in bright light. Three types of cone cells exist in your eye, with each being more sensitive to either short (S blue-violet), medium (M green), or long (L red) wavelength light. Each type of cell does not just sense one color, but instead has varying degrees of sensitivity across a broad range of wavelengths, but these various wavelengths are classified into the three categories. Human colour perception is most sensitive to light in the yellow-green region of the spectrum. Yellow is the result of the gree-sensitive and red-sensitive cones being activated.

The colour messages from the cones are relayed to the fovea at the centre of the retina.

The Brain

The brain assimilates the red, blue-violet and green impulses and mixes them up, joining information from the two eyes, to interprete the colour.

Most of what we see is based on the memory of a colour.

Some colours register more easily than others: Yellows and greens are perceived before other hues. Red and violet are the most difficult.

Perception Effects

Every colour in 2D space is affected by what us placed next to it. Perceiving optical colours often has to be learned – how to isolate colours from their environment and prevent interference from the brain.

Successive contrast
If one stares at a colour for some time then look away one sees the complement as a coloured glow. If there is no white space then we see a combination of the complement and adjacent colour.

Simultaneous contrast

Colours look very different depending on their surrounding colours.Complementary colours intensify each other and ‘sing’ or vibrate along their edges.

Outlining in white or black can deceive the eye into thinking colours are darker or lighter than they really are, and that there are more or fewer colours. If colours of equal or similar value are juxtaposed their boundary disappears. This can be counteracted by putting high or low value boundaries.

Colours can bloom into new colours depending on what colours are around them.

Transparency effects

Where one colour looks like a ribbon lying over another.

Bezold effect

The entire appearance of a design can be changed just through changing one colour.

Phantom colours

Produced by juxtaposition of hues.
Eg pointillism, divisionism and television screens.

Spatial effects

Hues that are lighter at maximum saturation (yellows, oranges) appear larger than those that are darker at maximum saturation (blues, purples)

When a colour expands in this way it may also seem closer to the viewer – warm colours advance but cool colours recede. But artists can bring any colour forward depending on what other spatial devices they use.

Spatial advancing or receding results from contrasts between colours. Hue and value contrasts are greatest in things close to us and less apparent in things at a distance. Where there is particulate matter forms also appear bluish because of scattering of short blue wavelengths in sunlight.

Colour Combinations: Harmony and Contrast

These optical effects help us to understand our reactions to particular colours and colour combinations.

Colour combinations are conventionally divided into:

Monochromatic : single colour with variations in value and saturation. Break up with patches of neutral colours. Use hard and soft edges making some shapes come forward, others back.

Analogous : low contrast uses several hues lying next to each other in a colour wheel. But what this means depends on which colour wheel is used.

Complementary : high contrast. The opposite colours hold each other in balance and intensify each other. But relative amounts affected by value ie red and green are equal, orange needs more blue, yellow requires even more violet. Mixes of complementaries reduces saturation and contrast.
Double complementary – 2 adjacent hues with their complementaries
Split complementary – colours to either side of complementary

Triadic:
3 colours equidistant. Can be interwoven with more neutral colours.

Tetradic:

4 colours equidistant. Can be interwoven with more neutral colours.

However designing colour combinations is far from a systematic process – there are many different colour wheels and variants of the primary colours. The effects of particular combinations are also highly dependent on prevailing fashions : cultural associations, which combinations the viewers have seen many times before and which seem new etc.