A way to quickly replace colors in FM?

I have a document which currently uses a Pantone green for a variety of paragraph styles, and I need to make the entire document black and white. I can delete the Pantone color in the color definitions, and replace each instance with black, but some of the colors like Magenta can't be deleted or edited.Is there a way to quickly find each instance of magenta and replace it with black, or do I need to go through and change them all manually?

Also, these magenta instances are all table heads (or first row at the head of each column, I suppose) and the magenta is the shading behind the text, not the text itself. I can't seem to find where that color is defined.