Fluorescent light bulbs can change color and lose brightness over time.
The study looked at how the light and color of compact fluorescent lamps change with different voltages and burning times. They tested 15-85 watt CFLs with color temperatures of 2700 K, 4000 K, and 6500 K. They found that the brightness of the lamps reaches a maximum at certain voltages, and the color temperature changes as the voltage changes. The color temperature decreases over time, especially for high-power lamps with high color temperatures. The color rendering index stays mostly the same.