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.
The same hair color dyes are used as are used in other permanent hair color products. Because permanent dyes contain hydrogen peroxide, they cover gray hair more effectively and can be used to lighten hair color, unlike other dyes. Underground Color is a semi-permanent hair dye, which means it won't wash out the next day. The law does not require that coal tar hair dyes be approved by FDA, as is required for other uses of color additives.
The solution of hair dyes does not allow for any, "gradual," color change when, and if, you feel it's time to do so. However frequent applications would be required to sustain the color as the dye fades with time, exposure to environment and regular washing of hair.
I use to dye my hair blue black and wanted to change it to red. When you color your hair the first time, you have to dye out your normal hair melanin color and replaced it with red dye. Therefore, some bats are marked with black hair dye and the other are marked with red hair dye.
You see that luscious red head on the hair dye box and you think, "Wow! I'm getting ready to do that to my black hair and dye it red on top of that. But the red color is not going to come out exactly as seen in the model of the Hair Dye box. As a rule of thumb, the color you will get depends on your natural hair color.
If you have dark hair, your red will come out a dark red, and if you have very light, or blonde colored hair, your red well come out flaming red! So, don’t always believe that you will be getting exactly the same color as portrayed in the box.