Lets go back to colors. First, is that you have to come up with a concept, you should know what you like and stick with it. Sure you can come up with electic design, where a lot of inspirations are rolled into one, but this is very hard to pull off. An experienced designer may have difficulty in pulling this off, much more a neophyte. So let's stick to one concept, a good basis for a design concept is your personality. If you are the laid back type, who doesn't like much clutter, it would be best to lean your design towards modern minimalist, or zen asian designs. If you are the artistic, energetic type, then a colorful more vibrant design will suit you. Lastly, if you are not sure yet, I suggest you go to the safe side, not too dull, but not too funky.
My rule of thumb is to use the half tone, this can go either way, its color but not color over all. Just a splash of it. Just a touch. Do not go over bored with the color that you might end up with a bedroom that looks like McDonalds.
If you are relying on a paint swatch, pick the 2nd tone from the darkest. So instead of choosing a vibrant red use the melon pink, just a notch from the darkest. You may still use the vibrant red, but be sure that it is just one wall or else it will be too overwhelming. Another thing is you can choose a favorite dress or bag, and use that as your basis, if you like the coordinates so much ang you have lived with it for a long time chances are it is good coordination of colors that will also look good on your wall.
Lastly have fun, if you chose the wrong color, what the heck you can paint it over.