Specific Color Ink

[Bridger Maxwell]

Hey,
  I have a need for an ink that makes an image visible ONLY if the color
beneath it is a specific color.  I was shooting for black, but I can work
with whatever color is possible.  I have a program where all empty space is
black.  This has advantages because it is very easy to move object around
without having to worry about how it fits into the background.  My thought
would be to have an image and an ink that shows up only where it is black.
Then I could give the black space a cool shiny black look (like frontrow),
or whatever else.  Any help would be greatly appreciated.  Also, is there
any way to access Core Image besides transitions?  Can we use the blend
modes or filters?

  TTFN
   Bridger