dispcal: 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/dispcal - from package: argyll

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

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