Color is the most striking and visually stimulating of all the plant design principles. Attention can be drawn to certain areas with color, and color can have a psychological effect on most people. For example, bright colors stimulate or excite, while cool colors tend to promote restfulness and relaxation. There are two types of color in a design composition. The second type of color is accent color, which is used to emphasize and draw attention to certain features.
Form describes the shape and structure of landscape plants or plant masses.
Every plant has a distinct form. General forms are rounded or globular, conical, oval, pyramidal, weeping, spreading or irregular. Horizontal and spreading forms add width to tall structures. Weeping forms tend to create soft lines and tie the building to the ground. Round and globular plants are good for creating large plant masses for borders and enclosures.