Following on from stakx’s Word 97 solution, here’s what works in Word 2010:
- Open the Find and Replace dialogue (e.g. Ctrl-H)
- Click in the "Find what" box.
- Format drop-down, Font, choose the Font color to be found, OK.
- Click in the "Replace with" box.
- Format drop-down, Font, choose the colour to end up with, OK.
- Observe that the Format: description for "Find what" and "Replace with" is now different.
- Replace/Replace All/Find Next as desired.
You can determine the original colour as follows:
- Click on a bit of text with the original colour
- Open the colour palette. If neither a "Theme color" nor a "Standard color" is selected, you may need to click on "More colors".