The Color2Gray plug-in allows you to show and print placed color bitmaps to grayscale without modifying the original color image. It works best for JPEG and TIFF images.
The original image is not changed and remains in color, yet it is output as a grayscale image. The gray image will only render on the black (K) plate.
Color2Gray is not simply stripping out the CMY plates. It recalculates a new K output based on the combined CMYK input.
Color2Gray is now compatible with InDesign CC and InDesign CC 2014.
More info here: