Proximity helps creates organisation. By grouping similar elements together or in close proximity, you create a relationship between those elements. It also provides a focal point and can give the reader and idea of where they should start and finish reading.
Proximity doesn’t mean that elements have to be placed together, it means they should be visually connected in someway.
Repetition strengthens a design by tying together individual elements. It helps to create association and consistency.
The consistent repetition of an element is widely used in interior design. Elements can be as simple as colour, shapes, typefaces or even texture.
Contrast allows you to emphasize or highlight key elements within your design. Contrast is created when two elements are total opposites. This doesn’t necessarily have to be colours either.