With so many colors and designs available, selecting the right finish just might be the most difficult part of your carpet-buying decision. Narrow your search by choosing shades that match the overall mood or tone you want to set for each room. Try cool blues or greens to create a calm, peaceful setting, and warm reds or golden shades to make a large space feel cozier. Light colors can make small rooms feel larger and more open, so try cream or tan if you're feeling claustrophobic.
Before settling on a neutral shade, decide whether you want your carpet to serve as a focal point or fade into the background. Only go neutral if your walls, furnishings orartwork serve as focal points, as this can help you avoid a plain, monotone design.
Dark shades or patterns can hide stains, as can tweed or textured carpet designs. To make patterned rugs work with other patterns in a room, stick to designs within the same color family [source: Schmidt]. For maximum versatility, use carpet tiles to create your own patterns and designs or to add a border around the perimeter of the room.
Always ask for carpet samples of each color you're considering. Try to get the biggest samples available, and take them home to examine them in natural light before you buy. Keep in mind that sun exposure can fade colored carpeting, so choose fade-resistant products if your carpet will be in direct sunlight [source: Carpet and Rug Institute].
Source : http://home.howstuffworks.com/