It really depends on how old your son is, and what he is like as a person. Personally I think blue is a bad colour for any room - it is very cold and unforgiving and tends to dominate. Why don't you ask your son what colour he would like? After all it is his room. He will probably choose a colour you hate, like orange, but you can always paint one wall in the colour he likes and do the rest in a neutral shade, or one of those shades which is white with a hint of colour - then if he chose orange, you could paint the other walls in a white with a hint of apricot or peach, and it would all coordinate well. If he's not old enough to speak yet, well, you can paint it any colour you like! Yellow encourages happiness, red aggressiveness.
