Non-dyed hair never has perfectly even color. Bleach is not a hair dye its more of a color strip. If you only want a 100% all natural hair dye then use the plant based henna hair color. Meanwhile, temporary dyes and highlight treatments should be able to color hair without the need for harsh chemicals.
More specifically, the question is which color of hair will hair dye affect the most. Never mix different hair dye products, because you can induce potentially harmful reactions (if not an unappealing hair color). White girls can dye their hair any color they want.