Just in case you are not very Photoshop literate: Open your image and double click the thumbnail in the layers palette. Now drag the thumbnail to the bottom of the layers palette and drop it into the new layer box to the left of the trash bin. Now click Image > Adjustments > Hue Saturation and pull the slider for saturtion all the way to the left. Now click Layer > Add Layer Mask > Reveal All. Select the brush tool and make sure your foreground color is black. Now "paint" in areas you want the color to show.If you goof and touch an area you don’t want color click X and it will give you white. Paint away your mistake and click X again and you will once again have a black brush. Once you have it the way you want flatten it and enjoy.