Here's why:

* The Speed of Light: The speed of light in a vacuum is a fundamental constant in physics, approximately 299,792,458 meters per second.

* Electromagnetic Spectrum: Visible light is just a small portion of the electromagnetic spectrum. This spectrum includes radio waves, microwaves, infrared radiation, ultraviolet radiation, X-rays, and gamma rays.

* Constant Speed: All electromagnetic radiation, regardless of its frequency or wavelength (which determines its color), travels at the same speed in a vacuum.

Let me know if you'd like to learn more about the electromagnetic spectrum!