The question of the Moon’s color is far more complex than a simple glance at the night sky suggests. Our perception is constantly filtered and altered by the conditions of Earth’s atmosphere. The Moon’s appearance shifts dramatically, moving from shades of muted gray to brilliant yellow, and occasionally to striking orange or deep red. To understand the true color of the Moon, one must separate its inherent surface characteristics from the variable effects of Earth’s air.
The Physical Color of the Lunar Surface
The Moon’s inherent color, seen without the interference of Earth’s atmosphere, is a range of dark grays and browns, not the bright white or pale yellow often imagined. The surface material is primarily regolith, a layer of fine dust and fragmented rock created by meteoroid impacts. This regolith is composed mainly of silicate minerals, similar to rocks found on Earth, but it also contains iron and titanium oxides.
The presence of these metal oxides, especially iron, contributes to the subtle brownish-red hues visible when the Moon’s color is enhanced in images. The dark areas, known as maria, are ancient lava flows rich in iron and titanium, making them darker than the brighter, aluminum-rich highland regions. Lunar samples returned by the Apollo missions confirm that the moon dust is extremely dark, closer to the color of charcoal than white sand.
The Moon reflects only about 12% of the sunlight that hits it, which means it is a relatively poor reflector. Against the blackness of space, however, even this small amount of reflected light makes it appear bright to the human eye. Images captured by astronauts on the lunar surface or by orbiting probes serve as the most accurate reference for the Moon’s true, muted coloration.
How Earth’s Atmosphere Changes the Moon’s Appearance
The most common colors the Moon displays—yellow, orange, and pale white—are direct consequences of light passing through Earth’s atmosphere. This effect is governed by a principle called Rayleigh scattering, which explains why the sky is blue. Short-wavelength light, like blue and violet, is scattered most effectively by the tiny nitrogen and oxygen molecules in the air.
When the Moon is high in the sky, its light passes through a minimal amount of atmosphere, allowing most of the color spectrum to reach our eyes, resulting in a familiar pale white or slightly yellow hue. However, as the Moon rises or sets and is low on the horizon, its light must travel through a much thicker column of air. This long path causes nearly all the blue and green light to be scattered away before it reaches the observer.
Only the longer-wavelength colors, such as orange and red, penetrate the atmosphere easily and are left to illuminate the Moon’s surface. The intensity of these warm colors is often amplified by terrestrial elements like dust, smoke, or pollutants suspended in the air. Large urban areas or regions affected by forest fires can have a greater concentration of these particles, leading to a deeper orange or red appearance even when the Moon is slightly higher in the sky.
Explaining Specific Color Events
Two named phenomena often confuse the understanding of the Moon’s color: the Blood Moon and the Blue Moon. The deep reddish-orange appearance of a Blood Moon is caused by a total lunar eclipse. During this alignment, Earth passes directly between the Sun and the Moon, blocking direct sunlight.
The only light that reaches the Moon’s surface during totality is sunlight that has been refracted, or bent, through Earth’s atmosphere. As this light passes through Earth’s atmosphere, the blue and green light is scattered away, leaving only the red and orange light to be projected onto the Moon. This effect is the sum of all the world’s sunrises and sunsets cast upon the lunar surface.
In contrast, the term Blue Moon has almost nothing to do with the actual color of the Moon. This label is a calendrical designation, referring to the second full moon occurring within a single calendar month. The Moon genuinely appears blue only on rare occasions, which can happen after major atmospheric events such as large volcanic eruptions or massive forest fires. These events inject large particles into the atmosphere that scatter red light, allowing the blue light to pass through and briefly color the Moon.