Many languages contain expressions that use colour metaphorically (common examples in English include "green with envy," "feeling blue," "seeing red," "purple passion," "white lies," and "black rage.") this can make it difficult then to translate these ideas in to other languages in different cultures.

Although the medical benefits are still in question, colour has been shown to cause definite physical and emotional reactions in humans and in some animals.

People who view a display of unusual colours produced by special illumination may experience headaches and nervous disorders; tasty wholesome food served under such conditions appears repulsive and may even induce illness.

Scientific evaluations have linked the sensations of relaxation or pleasure, tension or irritation, spirituality or passion to the influences of colour. A number of studies over the years have looked at the relationship between colour and emotions. This can have a number of practical applications. Children who are taught in a predominantly red classroom will become irritable. The impact of strong reds could be one reason why so many fast food chains are coloured red, yellow or orange. Studies suggest this stimulates the customers making them hungry yet impatient at the same time (New Idea, 20/06/92 p. 43 Colour Your World).

Understanding the psychological effect that light has on us is important in relating to light and colour. When light strikes our eyes, it stimulates a chain of events throughout the body. These reactions might be, a quickening of the nervous system, excitation or depressing, and effect of tranquillity etc. Feelings of irritation or pleasure may occur.

Some basics in colour theory involve the idea of "colour temperature", temperature being defined as colours that would be considered cool, warm or even hot.

Colours in the muted blue, green and violet range are considered as "jewel tone colours". They are "Cool colours" and are, restful, and tranquil for the eye. Warm colours would be defined as muted range of red, brown and orange. These colours are used to keep the mind stimulated and alert. Hot colours are yellow, pink, bright orange, and pure red. The uses of these colours are for the purpose of exciting the eye.

Hard Colours:
The hard colours are Red, Orange, and Yellow. Hard Colours are also known as warm colours, because of the warming effect they have psychologically. They also create a mood which is cheerful, energetic, vital and sociable. People may find them provocative, arousing and even erotic. The energy from these colours can provoke strong reactions.

Soft Colours:
The soft colours are blue, green, and violet. Soft colours are also known as cool colours, because of the cooling effect they have psychologically. They also have a quieting and relaxing effect, although they can be cold in some way if not lifted by something else.

Other Research shows:

Yellow: Is a mental stimulant, and stimulates the nerves. Emotional, positive, cautious.

Orange: Brightens the emotions and also stimulates the nerves. Deep orange has the most exciting influence. Emotional, positive, organic.

Green: Affects the nervous system, and is hypnotic and sedative. Lowers blood pressure. It is useful in cases of exhaustion, neuralgia, nervous irritability, anxieties, neurotic fears, and headaches. Has an overall calming affect (This is why green is used in operating theatres and on hospital gowns for its calming effect). Comforting.

Violet: Has the most subduing influence followed by purple.

Red: Danger, negative feelings, and excitement.

Blue: Light blue: Youthful, cool, masculine
Dark blue: Calming, trustworthy, stable, mature

Black: Seriousness, death, heaviness.

An alternative approach to dealing with emotions is Colour Therapy. One of the colour therapies is called Aura Soma.