Your first consideration when purchasing a new carpet shouldn't be color, as important as it is. Your first consideration should be how much traffic the carpet is going to receive. If you carpet is going in a bedroom it won't be receiving the same traffic that your living room carpet will receive. How stain resistant will the carpeting need to be? This is a consideration for any carpet, but especially carpeting that is going to be used in a dining room or playroom area where there is a steady stream of food or spill possibilities.
You'll want to ask about the rating of the carpet. Indoor carpeting is generally rated on a scale of 1 to 5, with 5 being the highest rating. A carpet with a rating of 5 is considered superior for heavy traffic area. A rating of 4 or above is considered outstanding and would be recommended for heavy traffic areas in the home. A rating of 2.5 to 4 would provide normal durability. Carpeting with a rating of 2.5 or lower should only be used in very light traffic areas, such as bedrooms. Choosing the carpet based on what type of traffic it will receive can help you save money in the long run. Buy the carpet suited to your needs.
The highest quality carpet you can buy would be a carpet made of wool. A wool carpet is a very expensive investment, but it will reap benefits over years of use as it will out perform any man made carpet. Just two of the benefits of a wool carpet are it's natural soil resistance and it's ability to retain it appearance, meaning it won't crush or wear down like man made carpets. Unfortunately, wool carpet is out of the reach of most of us. If you can't afford a house full of wool carpeting then have wool carpeting installed in the room that receives the highest traffic.
There are many different man made carpets to choose from. If you have a high traffic area, then nylon would be a good choice due to it's durability. Nylon is also stain resistant and repels mildew. A carpet of Olefin would also be a good choice for heavy traffic areas as it is strong and easy to clean. Polyester is also excellent in high traffic areas as it is easy to clean and resists water based stains. Polyester has the look and feel of wool, but is much less expensive.
Now to the color consideration. A light colored carpet will create an effect of a larger space. Of course, light colored solid carpets will show stains more easily. Dark carpets tend to absorb light giving a room what some would call a "cozy" feeling. Rugs with patterns will make a room appear smaller.
When you find a carpet you like ask to take a piece home. Look at the carpet during natural daylight and at night under artificial light as the color can change.
Careful consideration when purchasing your carpet can help keep you happy with your decision for years to come.