https://en.wikipedia.org/wiki/Black-body_radiation As objects get hotter and start glowing, they start to emit radiation in visible frequencies. Very hot objects keep glowing in the redder parts as they also start to glow in higher bands. Our eyes collect all the various frequencies at different intensities and experience them as one color. The second diagram on the page, with the chromaticity of different temperatures of ideal black-body radiators, shows the color that we perceive as the temperature of the glowing object goes up. The sun is around 5800k, so a little bit in in the yellow-green direction from perfectly balanced color response.

If you want to know why that diagram has its white point where it is, it's based on testing a bunch of people in laboratories. It's fairly predictable and repeatable, but it might not match your experience outdoors.