Light v. Dark
If you want to make a visual impact, you would want to install a floor that highlights a light and dark contrast. Dark floors really stand out against lighter wall colors while light flooring really brighten up a room with dark walls. When the wall and floor are extremely different, it tends to really highlight both as two totally separate features of the room. Keep in mind that very light and very dark flooring both tend to show dirt and dust easier than mid-tone wood floors.
The second approach is when you already have a neutral wall color (beige, gray, taupe, white and cream). Neutral wall colors work well with virtually any flooring color. Neutral colors with warm undertones (orange, red or yellow) look better with warm wood floors, while cool undertones (taupe/grayish) look better with cool wood floors.
The color wheel makes it easy to find a wall color and flooring color that will look exceptional together (see adjacent picture). When you look at the color wheel, colors that are directly across from each other are considered complementary. For example, floors with a red undertone, such as cherry, look pleasing with green wall colors. Floors with an orange undertone look delightful to the eye paired with wall colors in the blue family. Lighter floors with a yellow undertone are a great pairing for purples. Using this method is a great way to match wood flooring with wall colors.