A blood orange sun, typically seen during sunrise or sunset, is a result of atmospheric scattering of sunlight.
When we observe the sun setting, its white light travels through the Earth's atmosphere. The atmosphere scatters higher frequency light (like blue and violet), while lower frequency light (like orange and red) is transmitted more easily. According to the provided reference, "At sunset, when the Sun is lowest in the sky, and seen through the largest amount of 'air mass', we see it as an orangish-red color."
In summary, a blood orange sun signifies that you're seeing the sun through a thick layer of the Earth's atmosphere, usually at sunrise or sunset.
