Here's how to safely recolor any part(s) of any .WMF clip in PPT 2007:
You triggered something in me that led me to the way to do it. Thanks!
Technique:
1. Break any .WMF (gotta be .WMF) clip into a Microsoft Drawing Object by selecting the clip, clicking on Recolor, and answering Yes to break it into a MSFT Office drawing object.
2. Do not ungroup the objects or you’ll create a mess.
3. Select the individual object(s) that you want to edit, e.g. both whites of the eyes.
4. Use the Drawing Tools to modify the object(s).
5. Repeat Steps 3-4 for all objects you want to recolor. In my case I recolored the lion's:
o Whites of the eyes (Shape Fill with Color).
o Letters in the word “Leo” (Shape Fill with Texture).
o Outer band around the drawing (Shape Fill with Gradient).
Hope this helps. It should clear up the mystery--many folks claim you can no longer do it, but you can. In fact, it seems easier to me. 
Walter
Fort Lauderdale