Hi Brook:
My name is B. Delfin. I have a Bachelor's of Science in Interior Design (not Interior Decorator) and have studied and applied colors on decor with my clients.
First of all, I agree that you don't use pink. It's outdated and very predictable as far as design. I am more trendy and in most of the model homes that I see if I see a very pink color in a daughter's room I am usually turned off.
Here's my advice. If you are using your nice bedding with purple, little green, yellow and white use this piece as your theme. It would complement but not necessarily be the same all around. Remember to consider the lighting that goes to the room. If there are windows that lets the light in, you might not want very bright colors but use light green to make it soothing for the child and you. Use your decor such as stuffed aninmals, painting, etc. using the purple, yellow and white but do not overwhelm the room. Do not use paper borders(also outdated) but you can paint the lower portion of the wall with another color like white as a border. I have used two colors on the walls and they look pretty good and you can sample them next to each other when you go to Home Depot or Lowes.
If you need additional input, please feel free to e-mail me directly at ____@____.com