As the sun's rays pass through the Earth's atmosphere only the red light gets through. Is this the result of specific gases in the Earth's atmosphere filtering the red light? Does all of the nitrogen and oxygen affect the sunlight shining through it?

Let's say the Earth (or just about any earth-like planet) has an atmosphere made mostly of green chlorine. When the sun shines through the chlorine atmosphere and hits the moon during a lunar eclipse, would the moon appear green? Would different gases result in the moon becoming different colors?