Which of the following design principles involves creating a theme or pattern throughout a hairstyle?

Repetition in hairstyling design principles refers to the use of similar elements throughout a hairstyle to create a cohesive theme or pattern. This might involve repeating the same curls, layers, or color highlights at regular intervals, which helps to unify the overall look. By implementing repetition, stylists can create a sense of harmony and consistency that guides the viewer's eye and enhances the aesthetic appeal of the hairstyle. This technique can be particularly effective in showcasing the stylist's vision and emphasizing specific features of the hair, such as texture or color variations.

In contrast, the other principles such as contrast, progression, and alternation serve different roles in design. Contrast is about juxtaposing different elements to create visual interest, progression refers to a gradual change in elements to establish movement or growth, and alternation involves using contrasting elements in a sequential manner. While these principles certainly contribute to the overall design of a hairstyle, they do not focus on the theme or pattern in the same way that repetition does.