xcolmix: 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 Debian possible default full paths are:

/usr/bin/xcolmix - from package: xcolmix

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

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