Ahmed,
I suggest using a color blender called 'Back 2 Natural.' It's designed specifically to blend the color of a hair system to the color of your own hair. This is a great product and it's available form adfhair.com. You just put it on a comb and run it through your own hair where it meets the hair system and it will blend the 2 colors together.
Regards,
John
http://toplace.com/