colortest-python: 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/colortest-python - from package: colortest-python

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

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