I'm guessing this is what you're wanting to do.
  What I did:
Open the color picture in your program.
Copy or open the same picture on top of the 1st one.
Change the top picture to black & white.
Then, using the Eraser option, erase the areas you want to have color. I use an older version of Adobe PhotoDeluxe, but I'm sure you can do it in whatever program you're using. I'd say it's pretty much the same procedure. You're going to need two copies of the color picture, change the top one to b/w and just remove the areas where you want color. | 
