Colors represent departures from normal temperature.
If the earth can't get rid of heat as fast as new heat arrives, the earth will get hotter, which means that anything that slows the earth's ability to eliminate heat causes its temperature to rise. Since the earth is an isolated object, suspended in space far from anything else, the only way it can exchange heat with the rest of the universe is through thermal radiation the emission and absorption of electromagnetic waves. Heat flows from the sun to the earth via thermal radiation and from the earth to the depths of space via thermal radiation. The rate at which heat flows to the earth is determined mostly by the sun's properties. But the rate at which the earth radiates away heat is determined by the earth's properties.