How to patch images without color problem?

[Markus Neteler]

Hi,

 actually I have to patch a mosaic of aerial photos together.
 After rectifying them I want to have one big image
 containing all the others.

 But now I run into trouble because the colors of all pictures
 except one (the first I specified in r.patch) are wrong.

 Does anybody know how to patch images properly?
 That should be possible in GRASS!

 With regards
   
    Markus Neteler

 PS: New GRASS 4.2.1 version today (27.) at
     http://www.laum.uni-hannover.de/iln/grass/grass42/
      - Linux binaries and source code -