Monochrome Mixed Color?

Some of you may be used to using the Monochrome Mixer in Aperture or Photoshop or pretty much any program that can convert to black and white. It allows for a great control of local contrast, and I often save an image in black and white to avoid using masks fixing a high contrast image. But using Aperture's color controls, you can use the same Red, Green, Blue filters like in the monochrome mixer to adjust the luminance of the Red, Green, and Blue parts of an image separately.

The result: