On what factor does the colour of the scattered light depend?

When white light is incident on a yellow pigment,which color of light is not reflected?

$(a)$ 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?

When blue and yellow pigments are mixed and white light is incident on the mixture,which color of light is reflected?

$(a)$ How does the sky appear from the surface of the moon?
$(b)$ What is the cause of the blue colour of the ocean?

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.