rainbow3.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/rainbow3.lut - from package: eso-midas

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

Error in other languages:
rainbow3.lut: bevel nie gevind nie
rainbow3.lut: comandă negăsită
rainbow3.lut: comando não encontrado
rainbow3.lut: commande introuvable
rainbow3.lut: command not found
rainbow3.lut: käsku ei ole
rainbow3.lut: không tìm thấy lệnh
rainbow3.lut: komanda nerasta
rainbow3.lut: Kommando nicht gefunden.
rainbow3.lut: kommandot finns inte
rainbow3.lut: komut yok
rainbow3.lut: nie znaleziono polecenia
rainbow3.lut: níor aimsíodh an t-ordú
rainbow3.lut: no se encontró la orden
rainbow3.lut: no s'ha trobat l'ordre
rainbow3.lut: opdracht niet gevonden
rainbow3.lut: parancs nem található
rainbow3.lut: perintah tidak ditemukan
rainbow3.lut: príkaz nenájdený
rainbow3.lut: příkaz nenalezen
rainbow3.lut: команда не найдена
rainbow3.lut: командата не е открита
rainbow3.lut: 命令找不到
rainbow3.lut: コマンドが見つかりません