y4mcolorbars: 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/y4mcolorbars - from package: mjpegtools

You may install the required package with command apt-get install {package}
Error in other languages:
y4mcolorbars: bevel nie gevind nie
y4mcolorbars: comandă negăsită
y4mcolorbars: comando não encontrado
y4mcolorbars: commande introuvable
y4mcolorbars: command not found
y4mcolorbars: käsku ei ole
y4mcolorbars: không tìm thấy lệnh
y4mcolorbars: komanda nerasta
y4mcolorbars: Kommando nicht gefunden.
y4mcolorbars: kommandot finns inte
y4mcolorbars: komut yok
y4mcolorbars: nie znaleziono polecenia
y4mcolorbars: níor aimsíodh an t-ordú
y4mcolorbars: no se encontró la orden
y4mcolorbars: no s'ha trobat l'ordre
y4mcolorbars: opdracht niet gevonden
y4mcolorbars: parancs nem található
y4mcolorbars: perintah tidak ditemukan
y4mcolorbars: príkaz nenájdený
y4mcolorbars: příkaz nenalezen
y4mcolorbars: команда не найдена
y4mcolorbars: командата не е открита
y4mcolorbars: 命令找不到
y4mcolorbars: コマンドが見つかりません