The silver apples of the moon,
The golden apples of the sun.
— Yeats, “Wandering Aengus”
Why does everyone think the Sun is yellow and the Moon is white?
While the Sun often appears yellow when it is low in the sky, and even red in certain atmospheric conditions, its characteristic color is very close to pure white.
And exactly the same thing is true of the Moon; yellow or red at times, but basically white.
And if the Sun were yellow and the Moon white — well, then the Moon would look just as yellow as the Sun, since moonlight is only reflected sunlight. To call a non-radiant body “white” is simply to say that it is highly reflective of all wavelengths of visible light, but of course it can only reflect such light as shines on it. A “white” object illuminated by yellow light would indistinguishable from a yellow object.