Which factor does not change the ballistic performance of a projectile?

The factor that does not change the ballistic performance of a projectile is the bullet color. Ballistic performance is primarily influenced by physical and mechanical properties of the bullet, such as shape, weight, and velocity, as well as external forces like aerodynamic drag. These elements directly impact aspects like trajectory, stability in flight, and energy transfer upon impact.

On the other hand, bullet color has no effect on the bullet's flight dynamics or terminal performance. While it may have implications for factors like visibility, identification, or aesthetic preferences, it does not influence how the bullet behaves in terms of aerodynamics or kinetic energy. Therefore, bullet color is negligible when considering the fundamental aspects of ballistic performance, making it the correct answer.