Just because a suggested colour scheme can work well, doesnt mean that it will work well. The colours that are supposed to work well together may not necessarily look the same in every case. It all depends on where you are decorating.
Darker tones can make a room look smaller, so if you are painting a small room, this may be very undesirable. In the same way, lighter tones can make a room look larger, and so if you are painting a large room you may be running the risk of making it look unfilled. (Although an illusion of a large open space may be what you are aiming for). Different colours also give differing perceptions of space: Reds, yellows and orange have a high visual value and stand out, and can therefore make a room look smaller, whereas blues and greens have the opposite effect.
Another factor to consider that affects the perception of space is the amount of natural light entering the room. Rooms with large windows can more acceptingly be painted in darker colours. Artificial light is no substitute for daylight and can often give a yellow light which will make the colour look different to what you expected. The best way to prepare for this eventuality is to get samples of colours and put them under both daylight and artificial light to make sure you are satisfied.
By selecting colours bearing in mind the information above, paint can be used to manipulate your perception of the room very effectively. Small rooms can be made to seem less crowded and larger rooms can be made to feel more intimate.
Another trick is to paint vertical stripes in a room to give an illusion of a greater height. This can work well in a child's playroom.
If you have a narrow long hallway, make it seem wider by painting the longer walls a lighter colour than the shorter ones.
These things are all aspects of home decoration that many fail to realize the value of.