Why is the color temperature of energy-saving lamps 5500K?

Simple understanding: color temperature is the color of light. (The color of light emitted by black objects heated to different temperatures shall prevail.) See the middle part of the attached figure, which is the color temperature range of white light: the fluorescent powder used for energy-saving lamps emits light under the excitation of ultraviolet rays, and the fluorescent powder with different components emits different colors, so the formula can be adjusted and the color can be changed.