Professional Hair Colour How To Dye Hair Darker Using Professional Hair Colour?

How to dye hair darker using professional hair colour? - professional hair colour

I dyed my hair, sisters of one or two shades darker with a professional hair color, but you do not know what kind of developer to use. I know that if your hair lighter who say his death last three colors lighter than use a developer of 30%, but have no idea what it is the darkest death. Can someone explain it to me. Thanks