Your hair colour may change naturally over time, mine started out chalk white but ended up with less grey than when I started chemo. Your hair has had a rough time (like the rest of you) and recovery is more than just growing back. Texture and thickness may vary over time as well as colour. 6 months waiting is generally recommended. But you could investigate any hairdressers around you who uses organic (non chemical) dyes. Even then I'd be tempted to grin and bear it for a bit longer if you can but others may have started earlier with no ill effects. Best wishes.