What is that red thing on the head of Guanyin Tathagata? What's the point?

Guanyin and Buddha have light wheels on their heads and behind them, representing infinite light. In the Amitabha Sutra, it is mentioned that Buddha's light is all over the dharma world. In a Buddha statue or painting, there will be a red dot between the Buddha's eyebrows, representing the white hair between the Buddha's eyebrows, which can be endless and show the magic of the Buddha. These are all out of phase, which is the difference between buddhas and bodhisattvas and mortals.