Here are some ways to rephrase it depending on the context:
More polite and respectful:
* Tiene el pelo blanco y es mayor. (Has white hair and is older)
* Es una persona de edad avanzada con canas. (Is an elderly person with gray hair)
* Su cabello está encanecido por los años. (Her hair is grayed by the years.)
More descriptive and nuanced:
* Tiene un cabello plateado y una sabiduría que viene con la experiencia. (Has silver hair and wisdom that comes with experience.)
* Sus años le han dado un aspecto distinguido. (Her years have given her a distinguished appearance.)
It's important to be mindful of the language we use when talking about people's age and appearance.