Grey Hair Coloring Issues: Why Isn't It Taking?

Question
hi there,

My Sister in law is a hair dresser, just got her diploma, she's started colouring my hair to save me some cash at the salon.  My hair is very dark brown with approx. 80% grey(silver)roots, i'm a natural brunette, most would say my hair was black, problem is when she colours my roots it doesn't take, she uses a permanent salon hair colour 50ml of No. 4.0 mixed with 75ml 6% 20Vol cream peroxide as per manufacturers instructions but it still wont cover my greys.... arghhhhhhhhhhh!!!!  So annoying! My hair is not thick, its quiet silky and well cared for, we cant understand why the roots wont take the colour?
Can you help :) thanks in advance!

Answer
Valerie,
 This is a common issue and easily remedied. Often natural (or neutral) series of colours lack the warmth needed for good coverage of grey hair. What she wants to do is add some warmth, either with a warm natural series (not red) if her colour line has one, or some gold series in the same level that she uses now. This should add the warmth now lacking for better coverage. Also, increasing the timeing by 10-15 minutes will probably help as well.
Best of luck to you.
Stephe (hairman)