Why are the tips of a porcupines quills white?

The tips of a porcupine's quills are white due to the presence of a hard, keratinous structure that reflects light. This coloration may serve as a warning signal to potential predators, indicating that the quills are sharp and potentially harmful. Additionally, the lighter color can help in camouflage, blending into the environments where porcupines are found, thus providing some protection from threats.