Question: KGamma compiles, installs and works fine, but does not make the alterations on the display.
Answer: A graphics card and a XFree driver supporting  that feature are required. For example, framebuffer will not work.

Question: KGamma compiles and installs without problems, but I can't find a KGamma entry in KControl.
Answer: KGamma is not installed in the right path. You have to find out your KDE path and reinstall like that:
  ./configure --prefix="Your KDE path"
  make
  make install
For example, in Mandrake 9.0 and RedHat 8.0 the KDE path is "/usr", in SuSE 8.1 it's "/opt/kde3".
If this not work: Some distributions use a special (non KDE standard) directory to for the "kgamma.desktop" file. You need to move that file to this location. For example, in Mandrake it's "/usr/share/applnk-mdk/Configuration/KDE/LookNFeel/kgamma.desktop".