All objects emit electromagnetic radiation (like light and heat), and the amount depends on the temperature, with hotter objects emitting more electromagnetic radiation. A blackbody is just what it sounds like (an object that absorbs all light), and they emit electromagnetic radiation in a spectrum that only depends on their temperature. The effective temperature of an object is the temperature a blackbody of the same size must have to emit the same amount of electromagnetic radiation. The color of an object depends on its spectrum, and for stars, this is closely approximated by the spectrum emitted by a blackbody of the same temperature. Since we don't know the actual temperature of the Sun (we can't just stick a thermometer into the Sun, it would melt), we will have to approximate its temperature with its effective temperature. The Sun's effective temperature is 5778 K, and an object that hot would emit a spectrum that looks like the RGB color #fff0e9 (corresponding to a blackbody of 5800 K), which is the pinkish color shown here.
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