If a cloud appears yellow, what has actually changed regarding its physical properties?

Answer

Nothing has changed; the illumination source (sunlight) has been filtered by the atmosphere.

The perceived color change to yellow is due entirely to the illumination source being filtered by the atmosphere during long path scattering, not because the water itself changed its reflective properties.

If a cloud appears yellow, what has actually changed regarding its physical properties?
lightweathercoloratmospherecloud