When the moon looks orange or yellow, it’s just because the person looking at it is seeing it through more layers of air. When the moon is low in the sky, its light has to pass through more of the blue-absorbing atmosphere on its way to the eye. This is similar to how the sun looks orange or red on the horizon. By then, only yellow, orange, and red light will not have been taken in.
People often call a yellow moon a “Harvest Moon.” But the phrase is more about how it rises earlier in the fall, which gives us more light after dark during harvest time. The moon illusion is when this yellow colour makes you think that the moon is bigger or closer than it really is. It’s not the same as a supermoon, when the moon is closer to Earth.
