Negative space in painting or drawing is a space everywhere in place and between the subjects of a portrait. It may be deceptive when the space about a focus, not the subject itself customs an provocative or artistically important shape and such shape occasionally is used to artistic outcome as the physical subject of the image. Using of negative space will relief your mind to focus on the spaces and help to confound your brain – reasonably that tries to recognize the whole thing it sees.
I think because that's what their only resource was during that time and the items are actually were really useful like let's say grass, it's a good color to use for green.
