gcolor2: 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/gcolor2 - from package: gcolor2

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

Error in other languages:
gcolor2: bevel nie gevind nie
gcolor2: comandă negăsită
gcolor2: comando não encontrado
gcolor2: commande introuvable
gcolor2: command not found
gcolor2: käsku ei ole
gcolor2: không tìm thấy lệnh
gcolor2: komanda nerasta
gcolor2: Kommando nicht gefunden.
gcolor2: kommandot finns inte
gcolor2: komut yok
gcolor2: nie znaleziono polecenia
gcolor2: níor aimsíodh an t-ordú
gcolor2: no se encontró la orden
gcolor2: no s'ha trobat l'ordre
gcolor2: opdracht niet gevonden
gcolor2: parancs nem található
gcolor2: perintah tidak ditemukan
gcolor2: príkaz nenájdený
gcolor2: příkaz nenalezen
gcolor2: команда не найдена
gcolor2: командата не е открита
gcolor2: 命令找不到
gcolor2: コマンドが見つかりません