Red

Red is considered one of the most powerful colours because of its ability to be seen firs and closer than the rest of the colours. Moreover, the effect of red colour is physical, e.g. it stimulates us and raises the pulse rate, and giving the impression that time is passing faster than it is. Hence, careful use should be taken in account when using red in relaxation areas as well as in working places. Despite the fact that some people get aggressive under influence of red colour, the major part is finding it stimulating the appetite that makes it suitable for places with food consummation. Additionally, red draws attention and a keen use of red as an accent can immediately focus attention on a particular element.

Good for: dining rooms, kitchens (not for professional ones), cafeterias, fast food places, as it promotes sociable and lively feelings, and stimulates the appetite.
Bad for: hospitals, big areas at working places, predominant in bedrooms, baby’s rooms. It can be overpowering and lead to headaches. Either vary the shade, paint one wall red, or use it for accessories only.

Green

Green is simply the colour of nature and balance and can be used everywhere but in reasonable quantity. Greater attention should be made using yellow green hues, which are not appropriate for food places. Yet, green occupies more space in the spectrum visible to the human eye and is second only to blue as a favorite color. Green is the pervasive color in the natural world that is an ideal backdrop in interior design because we are so used to seeing it everywhere.
For interior color schemes, olive and sage greens seem to be appealing because of their neutral character. Lighter shades of both are easy to live with for a long time. Both combine well with many colors. Dark greens are favored as traditional banker’s colors like burgundy, ruby, and sapphire blue. Yellow greens and muddy greens are relatively unpopular.

Good for: bedrooms, living rooms; as a muted/lightened hues almost every place.

Bad for: too much green is thought to make people too complacent or too laid back. Inject some red or orange to counteract these feelings.

Yellow

Generally yellow is emotional colour and it is associated with sun and light. Scientific experiments show that people in yellow environment are  more optimistic and cheerful. But yellow is also colour of fear and anxiety, especially when it is overused. To use yellow or not highly depends on user preferences.
Buttery shades are easier to live with long term than bright, sunflower yellow. The range of yellows is vast and some lend themselves more readily to decorating schemes than others. Yellows also frequently prompt more opinionated feelings than other colors. People who like it, really like it and people who do not, tend to dislike it intensely.

Good for: kitchens, dining rooms or north-facing rooms, schools.

Bad for: a bedroom in its bright hues, places occupied by people with mental diseases. Yellow is thought to enhance feelings of emotional distress.

Purple

Purple embodies the balance of red simulation and blue calm. This dichotomy can cause unrest or uneasiness unless the undertone is clearly defined at which point the purple takes on the characteristics of its undertone.
Historically, purple is the colour of kings. It may arguably be the most opulent of colours, and often connotes mystery or spirituality. Purples run the range of the red-purple such as eggplant to the blue-purples of a summer sky at sunset. Saturated purple is a dense, dark colour that can provide a potent punch of color with great impact. As a tint, purple tends to lavender and is one of the daintier colours favored by many young girls. In certain shades, it can become a subtle, but very flexible neutral. In general, purple is not good as main hue in places with dynamic activities.

Good for: living rooms, bathtubs areas, bedrooms, spots for relaxation, beauty saloons.
Bad for: kitchens, working places (where concentration is needed), places wit food when used in its cooler hues. Tip: introduce a livelier colour for mental stimulation such as green or blue.

Discussion

The psychology of colour and how colour affects human behaviour is now a serious course of study at universities. Hospital rooms, classrooms, fast food restaurants and offices are painted in colours to influence the behaviour and mood of the people who use these spaces. Even the products on the shelves of your local supermarket have been packaged in colours carefully chosen to attract your attention and encourage you to buy. Therefore the psychological effect of colours has a great importance and it should be reviewed in details when designing an interior.

Back in the history, these effects hold true in all cultures and for all ages. In Islamic culture for instance, green and gold are the colors of paradise. Speaking of those who will enter paradise the Qur’an states, “ornaments shall be given to them therein of bracelets of gold, and they shall wear green robes of fine silk and thick silk brocade interwoven with gold (18:31)” and they will be “Reclining on green cushions and beautiful carpets (55:76).” These colors were chosen for their religious significance and have been associated with worship since ancient times.

For centuries Hindus practicing yoga have associated color with power centers, known as chakras, in our bodies. From the base of the spine to the crown of the head, these centers correlate to the spectrum and, in some cases, the qualities associated with them closely relate to the list of associations given previously. Red, at the base (survival); orange, at the sacrum (creativity); yellow, at the solar plexus (joy); green, at the heart (harmony); blue, at the throat (communication); indigo, at the forehead (intuition) and violet, at the crown (enlightenment).

In my opinion, people always have been looking for hidden meaning in the colours and they always have had one that has been changing during the centuries. In other words, there is no unification of the meaning of each colour. There is rather a social conception of that meaning which would help us to better understand  the clients and to choose colours  with awareness when designing