Because of the similar color schemes and subject matter this painting is an example of what principle of art

Without the specific details of the painting mentioned, I am unable to provide a definitive answer. However, based on the information given about similar color schemes and subject matter, this painting could possibly be an example of the principle of art known as unity. Unity refers to the visual harmony and coherence created in a work of art when all elements and principles are working together to create a sense of oneness.