rainbow4.lut: 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/lib/eso-midas/13SEP/systab/bin/rainbow4.lut - from package: eso-midas

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

Error in other languages:
rainbow4.lut: bevel nie gevind nie
rainbow4.lut: comandă negăsită
rainbow4.lut: comando não encontrado
rainbow4.lut: commande introuvable
rainbow4.lut: command not found
rainbow4.lut: käsku ei ole
rainbow4.lut: không tìm thấy lệnh
rainbow4.lut: komanda nerasta
rainbow4.lut: Kommando nicht gefunden.
rainbow4.lut: kommandot finns inte
rainbow4.lut: komut yok
rainbow4.lut: nie znaleziono polecenia
rainbow4.lut: níor aimsíodh an t-ordú
rainbow4.lut: no se encontró la orden
rainbow4.lut: no s'ha trobat l'ordre
rainbow4.lut: opdracht niet gevonden
rainbow4.lut: parancs nem található
rainbow4.lut: perintah tidak ditemukan
rainbow4.lut: príkaz nenájdený
rainbow4.lut: příkaz nenalezen
rainbow4.lut: команда не найдена
rainbow4.lut: командата не е открита
rainbow4.lut: 命令找不到
rainbow4.lut: コマンドが見つかりません