I rely implicitly on my hair stylist to decide what to do with my hair. I assume she will let me know when it’s acceptable to go grey. I am not remotely there yet. But I am quite blonde now, while my natural color was dark brown. it’s been gradual, probably over the last 20 years it’s been ligther. But as I told a friend whom I had not seen in a long time who commented on the blonde, it is much more forgiving when growing out than dark hair.
My elders tell me after age 70 one should consider going natural. I got lots of time yet.