xf86gammacfg: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/xf86gammacfg - from package: kdegraphics

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xf86gammacfg - from package: kgamma

You may install the required package with command apt-get install {package}

Error in other languages:
xf86gammacfg: bevel nie gevind nie
xf86gammacfg: comandă negăsită
xf86gammacfg: comando não encontrado
xf86gammacfg: commande introuvable
xf86gammacfg: command not found
xf86gammacfg: käsku ei ole
xf86gammacfg: không tìm thấy lệnh
xf86gammacfg: komanda nerasta
xf86gammacfg: Kommando nicht gefunden.
xf86gammacfg: kommandot finns inte
xf86gammacfg: komut yok
xf86gammacfg: nie znaleziono polecenia
xf86gammacfg: níor aimsíodh an t-ordú
xf86gammacfg: no se encontró la orden
xf86gammacfg: no s'ha trobat l'ordre
xf86gammacfg: opdracht niet gevonden
xf86gammacfg: parancs nem található
xf86gammacfg: perintah tidak ditemukan
xf86gammacfg: príkaz nenájdený
xf86gammacfg: příkaz nenalezen
xf86gammacfg: команда не найдена
xf86gammacfg: командата не е открита
xf86gammacfg: 命令找不到
xf86gammacfg: コマンドが見つかりません