We often forget that calling for peace is the most courageous act we can take. It's easy to call for revenge, to claim injustice, and to launch an attack. It's much more difficult to forgive, to call for peace, to lay down weapons.
An optical impression is produced on our organs of sight which makes us classify as light, half-tone or quartertone, the surfaces represented by colour sensations. So that light does not exist for the painter.