colorinterpolate: 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/share/circos/tools/colorinterpolate/bin/colorinterpolate - from package: circos-tools

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

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