I just read online this: Simply set the saturation to monochrome/black and white/vintage.
Overgaard says this:
How to set up color and B&W workflow side by side on Leica M9 and in Adobe Lightroom:
Leica M9: Set Compression to DNG+JPG Fine in the SET menu, then Color Saturation to Black & White in the MENU. Now the Leica M9 saves color raw and B&W JPG Fine of the same image to the card.
Adobe Lightroom: Choose the menu Lightroom > Preferences > General: Check the "Treat JPEG files next to raw".
Now Lightroom will show the color raw and B&W JPG Fine next to each other for future imports (if you want it to show this for previous imported photos, you drag and drop the relevant folder into LR and it will now import the JPG files that it omitted on the original import. It did import and and save them to the folder, but it didn't show them as previews (If you shoot other camera systems you may learn that they produce a JPG to do a preview on the camea's screen (in color), and Lightroom doesn't expect that you would want that JPG imported as the natural thing would be to work on the raw file).
In Aperture you can do the same, but be aware that in Aperture you must decide if you want to use the raw or JPG as master, or show both. You want both, of course, but if you shoot color, you should make sure it is the raw that is master, not the JPG.