Colour Blindness

Colour blindness is an important factor that must be taken into account in the design of colour VDU screens. About 8% of all males and 0.4% of all females have some form of colour vision deficiency. Table 10.6 shows the ways in which light seen by someone with normal vision as red, green, blue, or yellow would be seen by peo­ple with various forms of colour vision defect. The different descriptions are sim­plifications, but they do give an indication of the problems that may arise. People with reduced ability of the green receptors (nearly 5% of males and almost 0.4% of females) will experience yellow as green-red, and if the red receptors are inactive,

TABLE 10.6

How Colours Are Perceived by People with Different Colour Vision Defects

type of Colour vision defect

Red

Green

Blue

Yellow

Absence of colour receptors 0.003% men, 0.002% women

White-grey

White-grey

White-grey

White-grey

Inactive green receptors 1.1% men, 0.01% women

Red

White

Blue

Light red

Inactive red receptors 1.0% men, 0.02% women

Whitish

Green

Blue

Light green

Inactive blue receptors 0.03% men, 0.001% women

Red

Green

White

White

Weak green receptors 4.9% men, 0.38% women

Red

Light green

Blue

Green-red

Weak red receptors 1% men, 0.02% women

Light red

Green

Blue

Green-yellow

Weak blue receptors (very rare)

Red

Green

Light blue

Light yellow

a8% of men and 0.4% of women have some deficiency in colour vision. Source: Summarised from IBM (1979).

yellow is seen as light green and red as whitish. In the total absence of colour recep­tors, all light is seen as white, and the world is only experienced on a grey scale.

10.2.6 Meaning and Perception

Colours have different meanings for different individuals. Colours are often described as warm or cold, as calming or creating aggression. However, research has shown that there is no uniform way in which people interpret subjectively the characteris­tics of different colours. The meaning of different colours is constrained by cultural, social, and educational factors. This is also strongly affected by individual personal­ity. It is therefore almost impossible to give any general advice in this respect. There is, however, a certain tendency for the density of a colour to be associated with rising and falling. One could thus use different colour densities of blue to represent differ­ent gas pressures, and use different densities of red to indicate temperature levels.