Hi paco71. I have no experience of using blonde colours [my hair is a very dark brown/almost black] What product did you use ? Basically system hair tends to `grab`colour much faster than growing hair ...... I have used colouring products in the past [not on my present system] when the hair began to look a copper-ish colour after a few months. I would only apply/leave it on system hair for 3 minutes max. then rinse out and apply conditioner, but would have to leave it in the growing hair 15 to 20 minutes to achieve the same depth of colour. A tip --if you need to `lighten`a shade or two [having gone too `deep`] is to apply creme peroxide through the hair..that will lighten the shade or`water it down` for you. Colouring can be tricky --timing is the important issue....only a few minutes on the system, but much longer on growing hair.. 7 or 8 times longer. I hope that gives you an idea of what may have gone wrong for you .. why did you just not order system hair to match your growing hair rather than giving yourself `hassle`from the start ? Paul.