What are the problems using these visible light flashes?
Visible Light
Transmission of visible light flashes, such as a strobe light, would be unreliable because
other lights could be mistaken for the transmitted signal, or
another bright light could prevent the light flashes, or
visible light (and some invisible light) can be blocked by various obstacles, e.g., fog, heavy rain.
Light spectrum includes all types of light that travel from the Sun to the Earth,
Visible light is a small part of it.