What makes a harvest moon orange?

it usually occurs when the moon is near the horizon. The atmosphere of earth actually absorbs light in the blue range of visible light, thus making the moon apear orange or red. the atmosphere is also why the moon appears bigger near the horizon than it does in the middle of the sky. The atmoshpere actually acts like a lense magnifying the image of the moon. And yes, the moon also appears red during a lunar eclipse because of the dust in the air, but also because any light reflecting off of the moon was bent towards it by the atmosphere , thus filtering it into a reddish color.

As mentioned, the moon sometimes appears reddish when it's close to the horizon because of the light-scattering effects of the atmosphere, and pollutants in the air. There is only one harvest moon each year. It's the full moon closest to the Autumn equinox in the northern hemisphere (that is, closest to 21 September). The harvest moon has nothing to do with its colour close to the horizon.

the Moon tends to look orange or red when it is rising or setting because that's the time when the light has to travel through the most atmosphere to get to you. The effect is exacerbated when there are thin clouds in front or behind the Sun or Moon: the clouds themselves often glow bright pink as well, because they are so good at scattering blue light.

The moon appears orange nearer the horizon due to the refraction of light. The light has to travel thru more atmosphere to reach your vision.

Same as when the sun sets.

The Great Pumpkin