Curves won't easily do what you want. Use the Saturation control, or just convert to grayscale. When I convert to B&W I prefer to use the Fred Miranda actions; it's still a color image in reality and retains some of the warmth of a film B&W image. Curves is best for adjusting your contrast by setting a gentle "S" curve.
Check out Burce Fraser's Real World Photoshop book, or Martin Evening's book. Those are my favorite PS books & are aimed mainly at the digital photographer.