The surface of the Moon appears predominantly gray when observed from Earth, and this is due to the way light is reflected off its surface. The color we perceive is influenced by several factors, including the composition of the Moon's surface, the angle of sunlight, and the Earth's atmosphere.
The Moon's surface is covered in a layer of powdery dust called regolith, which consists of various types of rock and mineral fragments. The regolith reflects light differently than a solid, smooth surface would. When sunlight strikes the Moon, the regolith scatters the light in various directions, leading to an overall perception of gray.
The color we see also depends on the angle at which sunlight reaches the Moon's surface. During a full Moon, when the Sun is directly opposite the Moon in the sky, the sunlight hits the surface more directly, resulting in brighter and whiter illumination. However, when the Moon is near the horizon, the light has to pass through a larger portion of Earth's atmosphere. This atmospheric filtering can give the Moon an orange or reddish tint due to the scattering of shorter-wavelength blue and green light by the Earth's atmosphere.
Therefore, while the Moon's surface is not truly gray in the sense of having no color, the predominant perception of gray is a result of the way light interacts with the Moon's regolith and the atmospheric conditions during observation.