Recommended safe (natural) hair dye to use post chemo

Hi hope you are able to help please.

Finished chemo in November and have been advised not to use hair dye for 6 months after treatment. 

I've spent most of this afternoon doing internet research on safe, natural hair dyes that are vegatable/plant based.  I've a list of chemicals to avoid.

My hair is very salt and pepper and I don't want ro use harsh chemicals, even after the 6 month period is up.

Your  advice, recommendations would be very much appreciated. 

I have found during my research Holland & Barrett and Daniel Field products appear to be very popular.

Many thanks in advance. 

Lisa x