HueMatch - Freeware
HueMatch is a program that allows you to change the color balance of an image to match the colors of another reference image. Matching is done by adjusting the histograms of the images.
HueMatch is very useful if you have before and after pictures of a clinical case and the colors do not match. If you show these pictures side-by-side, the result is not very nice. See the pictures below:
[Before image] [After image]
With HueMatch, you can make the 'after' image look like the 'before' (or vice-versa) and the result will be like this:
[Before image] [After image] HueMatch was described in this paper:

Download
Version 1.2.0.2 (28/5/2005). File size: 539 KB.
Click here to download.
This is a one-file software. Just save anywhere in your hard disk (or on the Desktop) and double-click to run.

Notes
HueMatch is freeware. No user support is provided, but do not hesitate to email for assistance. Any comments, bug reports or suggestions for improvements are welcome.
Changes in version 1.2: You can now copy and paste images from PowerPoint:
Select the image in the PowerPoint slide and copy it. Then go to HueMatch and paste it in the upper or lower frame. After changing the colors, copy it from HueMatch and paste it back on the PowerPoint slide.

Screen Shots
Second image matched to the first, to give the third:
[Screen shot]
First image matched to the second, to give the third:
[Screen shot]