This is a great, general way of doing weathering effects. Works on anything!
This is a great way to provide weathering effects on armor, tanks etc. Note that the choice of second paint is based on the model you are painting, the Calgar Blue here is just an example. This second color should be your highlight color for the specific model.
This is essentially green fire.
This not only works on swords, but any other Nurgle weapon or armory.