C:\> C:\Program Files\Oralce\VirtualBox\VBoxManage list vms
"OSX El Capitan" {31f0e8c6-48b9-4d3a-a533-64cc41a920cd}
C:\> C:\Program Files\Oralce\VirtualBox\VBoxManage setextradata "OSX El Capitan" VBoxInternal2/EfiGopMode 3