Hi, if you are going to do it with a box colour you would be far better ringing up their own manufactures helpline the number should be on the box , they would be far better to advise you as box colours are not what professionals train up with
box colours are a whole different ball game they usually only have one standard peroxide strength for all , and they don't state what that is ...
we are trained to mix up our own professional colours and strengths of peroxides accordingly for the hair type
if you look at the box they never usually tell you what strength of peroxide is in there which I think is very bad for the hair ,
give the box manufactures a ring about it all ... or go to a salon or college they love to get hair colour models in and are very well supervised good luck :hug: x minky