There are a few things you can do to invert colors on a photo on your iPhone. The first is to open the photo in an image editor such as Photoshop or GIMP. Then, use the following steps to invert the colors:

  1. Choose Edit > Invert Colors.
  2. Invert the colors using the sliders on the left side of the dialog box.
  3. Save the photo and enjoy your inverted color photos!