Client is 100% grey/white, fine hair. I have been low lighting hair for 5 years. After color is rinsed out it is a level 6N. I do 3pts of dk brown to 1 pt dk drabber with 5 minutes under dryer. The last year the color has washed out to a light golden blonde. What can I do to achieve a longer lasting color, client comes in every 10 weeks for appt. I need to reorder color soon.