The easiest way to do this is this:
-bring the image into Photoshop
-if the image is locked unlock it and make a copy of the image layer
-click the top image layer > go to Image > Adjustments > Black & White -- your top image layer will now be in black and white
-highlight the Black and White effect layer and the top image layer > control click and do Merge Layers
-look to your left where your tools palette is and find the Quick Selection Tool or hit W on your keyboard - this tool will allow you to make a selection in your black and white image - go ahead and select what you want to be in color - to unselect a part hit Option click (for MAC) or Alt click (for PC) - to deselect from the entire selection hit Command D (for MAC) or Ctr D (for PC).
-once you're done with your selection hit delete - you should see the color from the bottom image layer pop through the black and white layer - what you basically did here is you deleted a piece of the black and whit image layer and made a hole showing the layer under (the color image layer) - to refine the color cut out use the Eraser tool and erase on the black and white layer - you can merge the layers again when you're done and save it as a PNG file (sharper quality) or Jpeg if it's for web.
That's the easiest way to do it. Hope that helps!
