rgbpaint: 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/rgbpaint - from package: rgbpaint

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

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