How does number of hours of daylight affect the color change of poinsettias?

The color change in poinsettias is influenced by the number of hours of daylight due to their photoperiodic nature. Poinsettias require long nights and short days (typically around 12-14 hours of darkness) to initiate the blooming process and develop their vibrant red bracts. As the days shorten in the fall, the extended periods of darkness signal the plant to produce pigments like anthocyanins, leading to the characteristic color change. Thus, manipulating light exposure can effectively control their flowering and color display.