To add to Spruce's comment, the image you posted has so few pixels that if you project it onto a screen in your presentation, it's likely the viewers will see every square pixel. So, if you hve a larger (ie, more pixels) version of the same composite, why don't you post that so we don't waste our time modifying something that can't be used anyway.
In fact, if you have the individual component images that were used to create that composite, you should simply post them individually. Doing this would have the side benefit of allowing us to separately adjust the skin tones to (a) be more accurate, and (b) match each other.
T
PS - Just to be certain of what you mean, when you say, "the smaller of the two large heads", I presume you mean the bright one in the lower left corner, smiling and facing the camera?
