Which of the following factors is NOT influenced by bullet design?

The factor that is not influenced by bullet design is the color of the bullet. Bullet design primarily focuses on features that impact the bullet's performance in terms of its functionality. This includes how a bullet expands upon impact, penetrates materials, and transfers energy to the target—all of which are critical in determining the efficacy of a bullet for a specific purpose.

In contrast, the color of the bullet is largely an aesthetic aspect or a manufacturing consideration that does not affect its ballistic performance. While color can be important in certain contexts for identification or branding, it does not influence how the bullet interacts with the target in terms of expansion, penetration, or energy transfer. These performance-related factors are directly tied to the materials, shape, and construction of the bullet, which are critical for achieving the desired outcomes during use.