A lunar halo is caused by the refraction, reflection, and dispersion of light through ice particles suspended within thin, wispy, high altitude cirrus or cirrostratus clouds. Notice the Orion Constellation to the lower-left of the Moon.

Taken with a technique called High Dynamic Range, you can see both the sunlit part of the Moon and the dimly lit Earthshine lighting up the dark portion. I added the stars, taken on another night, to the background.

Though the Moon is mostly colorless, there are slight variations in the sunlight reflected by different regions because of differences in chemical composition. These small variations are digitally enhanced revealing the white lunar highlands have minerals composed of silicon, calcium and aluminum. The lowlands were formed from massive impacts, while cracks in the crust have allowed lava to flow up and fill in the basins, creating the lunar maria (seas). The cooled lava basalt's are often rich in titanium, which reflects more blue light, and iron, which reflects in the red. This image has been processed to show the blue titanium minerals.

Though the Moon is mostly colorless, there are slight variations in the sunlight reflected by different regions because of differences in chemical composition. These small variations are digitally enhanced revealing the white lunar highlands have minerals composed of silicon, calcium and aluminum. The lowlands were formed from massive impacts, while cracks in the crust have allowed lava to flow up and fill in the basins, creating the lunar maria (seas). The cooled lava basalt's are often rich in titanium, which reflects more blue light, and iron, which reflects in the red. This image has been processed to show mostly the red iron content.