Coloring of fawn Great Dane puppies

Question
I am looking to purchase a fawn male Great Dane and a majority of those that I have seen have a "dirty" or dark appearance on their chest and/ or back.  I have been told by a couple of breeders that this is all but disappear and turn to the desired golden coat as the puupy ages.  Is this true and if so, to what extent will they lighten?  At what age should this change be complete or to a point that no further lightening of the coat should be expected?

Thank you for your help and understanding.  

Answer
The smutty appearance is due to black hairs in the coat and I have never known it disappear.  The coat may darken as the puppy coat is lost at about 10 months.

If you don't like the smutty fawn colour find another litter where the colour is pure fawn.

K