i use feng shui in all the rooms of my house! for a while i gave it up because of what people above are saying, it tended to disrupt the general theme of my room. recently, though, i figured out that achieving feng shui is very easy when you use items that go on top other items or on the walls. they don't overwhelm the main colors of the room since they're so small, and they beef up your HHA score considerably (which makes me happy)
green goes to the south: this is the easiest one to do, i always put plants at the bottom of the room or something of the sort.
red is the hardest because usually people's rooms aren't red, and the right side of the room is always tricky for me to begin with. for this reason i usually use red flowers or red fruit, they look tasteful and quaint
yellow goes to the left and there are many more small yellow items than red, i think. same principle goes, though: yellow flowers and lemons make this easy.
feng shui doesnt appeal to everybody but i think it adds another level of satisfaction to the interior design process. there are red, green, and yellow items that can fit to any theme and make your room really pop! its a fun challenge in my opinion