One final example using a red-gelled light behind Tiffany will be shown:
For this example, a Deep Yellow filter was applied:
As is expected, the red background has turned orange. Here is the semi-black and white:
The background and skin now have a subtly-different look to them. The background is mauve, and the skin light brown. In this instance, the layer opacity of the black and white layer was set to 80%.