The most important factor when pairing a wall paint to a hardwood floor is that the colour of the paint must match the brown of the floors. Hardwood floors come in a variety of different colours and tones. Some woods are dark, others blond; some are warm, while others are cool. The tone of your floor will entirely affect the tone of your walls.
In general, blue walls will complement blond hardwood floors better than dark hardwood floors, although this depends upon the blue and the floors. The cool of the blue colour plays off of the warmth of the light yellow floors. Blue and yellow are complementary colours, which makes them stand apart from each other in attractive ways while still appearing related to each other.
Olive and sage greens tend to work well with medium- to dark-coloured floors. This is because the green, earthy colours usually look best with other tones that closely resemble earth itself. Still, some medium-toned greens will also work with some lighter coloured hardwood floors. If it is important to you to incorporate green into your walls, compare swatches on your walls and paint them low to the ground, so you can compare them to the floor.
Dark brown floors will look better with light brown or beige walls, while light brown floors will work with warm-hued medium beige walls of a slightly darker shade. When matching browns to each other, remember that if your floors are a warm colour (with yellow or orange), use a warm brown for the walls. If your floors are a cool colour (a greyer or darker brown), then use a cooler brown for your walls, as well.
Cream--not white--is the fallback for any home with hardwood floors, especially if you're unable to decide on a colour. Cream will match just about any hardwood floor colour. Cream is especially striking when placed against dark hardwood floors, because the contrast is so intense.