Red and yellow and pink and green... Lucas Hollweg on the cheap and easy way to transform a living space
Interior designers are always telling us that colour is one of the easiest, cheapest and most effective ways to transform our living space. But it is all too easy to get it catastrophically wrong, which is why many of us are nervous about using colour. Things may have moved on since the days when people played safe with magnolia, but, for most of us, the idea of vibrant, wall-to-wall colour is still a terrifying prospect.

And why shouldn't it be? After all, colour is a complicated thing. It takes a confident eye to make it work and disasters are almost as common as success stories. A friend of mine once painted large orange squares on the walls of her hallway, a look she had copied from the pages of a design magazine. The first time I visited her the paint was dry and she was almost in tears.

Jill Georgalakis, director of the Inchbald School of Interior Design in London, believes that a common mistake is to choose colours according to your likes and dislikes, without giving proper thought to the kind of mood that they will conjure up. "You should always start by identifying what you want in terms of atmosphere, bearing in mind that oranges, reds and yellows are warm, while greens and blues are cooler. Then think about whether you want something light or dark. You also have to ask yourself whether you want the space to be dramatic, with strong contrasts of colour, or calm, in which case there will be very little contrast."

Stylist and interior designer Janie Jackson favours the light and calm approach. In her West-London home, she has used a pared-down palette that is subtle but bright. "Colour is a very personal thing and everyone has their own palette," she says. "I use colours that are pale in tone - I can't deal with heavier tones, which I find a bit oppressive." Jackson's colours are pastels, but they are a far cry from the sickly, candy shades normally associated with the word. "I love them," says Jackson. "Old English houses often mixed these kinds of pale, pastel colours with gilt, and Swedish houses use them in very simple surroundings. They give a luminosity to a room and are very mood-enhancing."

Jackson describes her pared-down use of colour as "minimalist." Although pale, the shades she uses are rich in pigment, giving a look that is pure and bright, rather than washed out. The sitting room is typical: walls in calming eau-de-nil blue, wafting, pale-lilac, linen curtains, l9th- century chairs covered in pinky-red cloth and a mantelpiece on which stand swirling, sugar-candy-shaped, red and clear glass vases.

The rest of the house is painted in similar colours - that glow discreetly, rather than overpower. To make the most of the available light, the basement kitchen is painted a colour midway between lime and pistachio, combined with a table-top in peppermint green. The spare bedroom is a gentle lilac and the dressing room a fresh, slightly greenish yellow. Admittedly, the main bedroom is white, but even here there is evidence of Jackson's light touch. The white is more soft than brilliant - "slightly mushroomy" as she puts it - and soaks up the prodigious light from the windows, reflecting it onto the yellow walls of the dressing room next door.

Jackson claims, only half-jokingly, that with colour there are "never mistakes, just experiences". Georgalakis agrees. "I don't think there is any colour that doesn't go with another," she says, although she admits that there are certain rules about what does and doesn't work in a particular space. A colour that adds warmth to one house may simply look dingy in another.

"You can't separate colour and light," says Georgalakis. "If you have tall thin windows, the light will be completely different from that from a wide, low window. It's also a question of quantity. If a room is blue with spots of yellow, it will probably work, whereas if you have blue and yellow in equal quantities, you might well end up with a terrible mess."

Colour is so problematic because there is no such thing as a definitive colour. Green, for example, comes in infinite variations - lime, apple, emerald, peppermint. Red, too, can range from a vivid scarlet to deeper crimson and earthy terracotta. According to Inder Jamwal, design director of paint and wallpaper-makers John Oliver, the key lies in the tonal value of the colours you choose, rather than the colours themselves. "You can use totally contrasting colours, but if they are all of a similar tone they will work," he says. "If, however, you use pale and dark tones together, you will end up with something that is visually uncomfortable."

The London home of hat and cushion designer Victoria Savage and her husband Michael, who makes furniture, supports Jamwal's point. With white walls as a backdrop, the couple have used colour combinations which more conventional decorators would have probably avoided. But it works. "Most of the colours we have used have the same tonal value, which is why they go together," explains Victoria.

On the stairs, there are squares and rectangles of pink, orange, green and purple, while in the kitchen two alcoves are painted in contrasting shades of purple and green. "We just try it and see what happens," says Victoria. "The idea is that as you look through the house, you get glimpses of colour, but I am also very aware of the way the different colours reflect light onto the white walls around them."

This awareness of context - the way in which a particular colour interacts with its surroundings - is an essential part of using colour successfully in the home, according to Jamwal. "You should never view a colour in isolation, but in association. This is where people go wrong. They come in with a swatch of colour for us to match, but it doesn't work when they put it on their walls."

Similarly, it is wrong to assume colours that work in one setting will do so out of context - think of the vivid fuchsias of India or the rich blues and greens of North Africa, which rarely have the same impact in the cooler British light.

That said, Jamwal believes that colour should be fun. John Oliver's paints, which have enjoyed a cult following with everyone from society decorators to pop stars since the company started in the Sixties, have always played for laughs, with names like Purple Heart, Kinky Pink, Golders Green, Dorian Grey, and Psychedahlia (vibrant yellow). Give us a go, they seem to say, and see what happens.

As Jamwal explains, "At the end of the day, decorating should be a happy experience."