Turn Your Color to Black & White
If you have a color photo or artwork in color, that you’d like to turn black and white, but want to keep a color copy around here’s an easy tip.

With your art in view, drag a square or circle or any shape over the color art.

Color your shape with a any shade of gray.

Open your Transparency palette (Window->Transparency) and choose Color from the blend menu.

Now you have a converted black and white image wit your color art safely underneath.