Which phenomenon of light is responsible for the Tyndall effect?

Explain why,when the sun is overhead at noon,it appears white?

What would have been the colour of the earth's sky if there were no atmosphere?

At noon,the sun appears white because:

What is meant by scattering of light? Mention the factor on which it depends. Explain why the colour of the clear sky is blue? An astronaut in space finds the sky to be dark. Explain the reason for this observation.

$(a)$ What will be the colour of the sky in the absence of an atmosphere?
$(b)$ Why are traffic light signals (or danger signals) of red colour?