Accent walls can really tie a room together. If done properly, they can balance out narrow rooms, provide a conversation piece, and add an artistic flair to an otherwise drab room. However, there are a few do's and don'ts that must be kept in mind if you are to make the best decision regarding exactly which wall in a room should be chosen, and what the best colors are for your particular choice.
If you are choosing to paint an accent wall in a narrow room, then keep some basic color theory in mind. Warm hues like reds,yellows, and oranges will draw focus to a wall, effectively creating the illusion of being "drawn toward" the color. Therefore, if you were to paint the shortest wall farthest way from the entrance a bright red, then it will appear that the room isn't as narrow as it once was. However, if you were to choose one of the longer walls, it would only serve to make the room appear even narrower than it once was.
In contrast, cool hues like blues, purples, and greens can have quite a different effect. Cool hues tend to draw one's gaze away from a wall, thereby making a room or area look larger than it really is. These colors can serve to make short rooms appear longer, skinny rooms appear wider, and hallways appear more spacious.
Next, we'll talk about natural lighting. Warm hues work best in northern and eastern-facing rooms, as the amount of light that these are getting will be significantly less than the amount of light coming into your southern and eastern-facing rooms. Save the cool hues for the brightest rooms.
Visibility of your accent wall is another big factor to consider. If you are painting a smaller wall, then decorate sparsely. You don't want decorations or furniture cluttering up your accent wall and preventing it from doing its job. Working with your architecture is also important. If you have an irregularly-shaped wall in a room, then try if you can to make it your accent wall.