EcoColors is a permanent hair color formulated with nontoxic in mind. Perform an allergy test according to kit directions before applying any new color to your entire head. Allergies aren't to be taken lightly. Some allergies develop over time with repeated exposure. Just because EcoColors is p-phenylenediamine (ppd) free, doesn't mean you won't react. There are other oxidative dyes present in nontoxic amounts that some individuals may be allergic to. Make sure to have a plan in place with your physician in case you do experience any kind of allergic symptom. The color can be translucent on grays but will also affect the non gray hairs and possibly lighten them depending on the porosity of your hair and the desired shade you are trying to achieve.