If you have been dyeing and the regrowth is too dramatic:[]
Go lighter with overall colour or highlights.
Grown out all the dyed hair and cut off the leftovers. It's a tough transition but for many it's worth it to get off hair dye.
If you haven't been dyeing:[]
Add highlights gradually or as needed.
Go lighter with overall hair colouring.
If hair is already mostly or fully grey, use a toner.
Consider Henna dyeing, as you wash it will gradually fade, is safer and less harmful compared to other dyeing options. Use when first signs of grey are showing but do not use if hair is already mostly or fully grey, results may be too intense.