I've Taken Lot's of Medication Due To Illness

I've heard that when you take medicine for a good while it leaves a deposit on your hair and that it affects the color you put on your hair.  I haven't been satisfied with my color for quite awhile now, so I think this must be true!!!   Is there something I can put on my hair to remove the residue  before I color......so that the color will be true.....and   be   

be-U-tiful  .  I really appreciate  any and all help.......I'm new here!!!

Thanks,

Artihopeful  De De

To prove my statement... look at the ingredients on a hair dye box. The chemicals that it contains can barely be pronounced. These chemicals rob the hair of any nutrients and damage the hair permanently.

On top of that, a few of these chemicals have been proven to cause cancer(especially dark chemical dyes) and are linked to other conditions as well.

Henna has been used to dye hair for thousands of years in India and the middle east and Asia. It works by dying the keratin in the hair naturally.
Using henna also benefits the hair/scalp health.
Texture, shine,  and body all benefit.
More women should be aware of this and I'm surprised they don't.

Dozens of companies online sell henna around $8 and you get multiple uses out of one box.