@slhice shares some very interesting photo manipulation techniques that would let you change the colors and backgrounds of photos right inside PowerPoint without requireing Photoshop.

You may also like:

  1. Edit Clip Art Images inside PowerPoint Presentations
  2. Edit Photos on the iPad with Photoshop Express
  3. Remove Backgrounds from Photos without Photoshop
  4. Edit Digital Photographs and Images Online
  5. Edit Videos with PowerPoint 2010