The painting you are describing could be an example of the principle of harmony in art. Harmony refers to the pleasing arrangement and combination of elements, such as color, shape, and subject matter, that creates a sense of unity in a work of art. When similar color schemes and subject matter are used, they help to create a cohesive look that can evoke a specific mood or theme.
If the painting also contrasts certain elements or explores different themes while maintaining a sense of coherence, it might additionally represent unity. Both concepts are vital to the overall effectiveness and impact of a piece of artwork.