i have to dye my hair again...

its naturally black..or well i would say so brown it looks black really.
anyways...i have to color all the white hairs on my head..they have become increasingly more over time. The top of my head has the most but seems when i pull it back in a ponytail it seems like a head full.
my questins are
at what point does one embrace the grays/whites/mix?
and how do you go about the change just let it happen naturally? dye it that color and let it blend in?
i know its personal preference
what would/did you do?