gcm-picker: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/gcm-picker - from package: gnome-color-manager

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