According to our current understanding of physics, the speed of light in a vacuum, denoted as "c," is an absolute limit. In the theory of relativity, which is a well-tested and established theory, it is postulated that no object with mass can travel at or faster than the speed of light. This includes light itself, as light consists of massless particles called photons.
So, in short, light cannot travel faster than the speed of light (c). If it were to somehow exceed this speed, it would violate our current understanding of physics.
As for visibility, light is the range of electromagnetic radiation that is visible to the human eye. The speed of light determines how quickly electromagnetic waves, including visible light, propagate through space. Since light always travels at the same finite speed, it can be detected and observed within the range of that speed. However, it's important to note that the perception of light and visibility depend on various factors, such as the intensity of the light, the sensitivity of the observer's eyes, and the presence of any intervening objects or media that could affect its propagation.