The Moon, often romanticized as a silver or white orb, presents a varied palette of colors to observers on Earth. Its perceived hue changes dramatically, influenced by two factors: the Moon’s physical composition and the way light interacts with Earth’s atmosphere. The true color of its surface is a muted, deep tone, far from the bright white we usually see. These differences in appearance mean the Moon can cycle through a spectrum of colors, from subtle shades of brown and tan to the striking reds and blues of rare celestial events.
The Moon’s True Physical Color
The Moon’s inherent color is determined by the material covering its surface, a pulverized layer known as regolith. This fine, dusty material is the result of billions of years of meteoric impacts grinding down the lunar rock. Without a substantial atmosphere to scatter light, the Moon’s surface would appear to the human eye as shades of dark grey, brown, or a muted tan.
The subtle coloration is tied directly to the minerals present in the regolith. The brighter highland regions are rich in the mineral plagioclase feldspar, which is high in aluminum. The darker, smoother areas, called maria, are basaltic plains rich in iron and magnesium. These darker regions also contain high concentrations of iron and titanium oxides, which lend a deeper, brownish-grey color to the surface material.
Variations in the concentration of these elements create the faint color differences visible in high-resolution lunar images. Areas with higher titanium content reflect slightly less light, appearing darker than surrounding regolith. These compositional differences only produce a range of dark, earthy tones, confirming that the Moon is fundamentally not a white or silver body.
Everyday Apparent Colors
The Moon appears bright white, yellow, or orange on most nights because of how Earth’s atmosphere processes the reflected sunlight. When the Moon is high in the sky, it appears its brightest and whitest because its light travels through the least amount of atmosphere. Scattering of light is minimal at this angle, allowing nearly all wavelengths to reach the observer’s eye.
When the Moon sits low on the horizon, the light must travel a much longer path through the atmosphere’s denser, lower layers. This extended journey causes a phenomenon known as the “Horizon Effect.” Atmospheric gas molecules preferentially scatter away shorter, bluer wavelengths of light through Rayleigh scattering. Only the longer, less-scattered wavelengths—the reds and oranges—are left to reach the eye, which makes the Moon appear yellow, orange, or even deep red.
This effect is similar to how the sun appears reddish at sunset. It is often amplified by larger particles like dust and pollution, which contribute to Mie scattering. These larger particles increase the overall scattering, further filtering the moonlight. The Moon’s color changes based on its altitude and the current dust and moisture content of the air layer between it and the viewer.
Transient Colors from Specific Events
Some of the most dramatic lunar colors are temporary, resulting from specific celestial or atmospheric events. The most famous of these is the Red Moon, or “Blood Moon,” which occurs during a total lunar eclipse. This deep red color is caused by light from the Sun being refracted, or bent, by Earth’s atmosphere onto the Moon’s surface.
During a total eclipse, Earth blocks all direct sunlight from reaching the Moon, but a ring of light still passes through the planet’s atmosphere. As this light passes through, the blue and green wavelengths are scattered away, leaving only the red and orange light to be bent into Earth’s shadow. This filtered, reddish glow illuminates the eclipsed Moon, making it appear coppery or blood-red, with the exact shade depending on the amount of dust and clouds in Earth’s atmosphere at the time.
A truly Blue Moon, distinct from the calendar-based definition, is an extremely rare atmospheric phenomenon. This color appears when the air contains an unusual concentration of particles slightly wider than the wavelength of red light, such as from a large volcanic eruption or a massive forest fire. These specific-sized particles scatter the red light away, allowing the shorter, bluer wavelengths to pass through to the observer. This selective scattering creates a genuinely blue tint to the Moon, a visual spectacle.