She is definately a light color, but it does look different from her gold -- so maybe just a very light silver? Does the owner have a picture before puppies that really shows the coat well? Just as important as the colors themselves is placement of the colors. You do not want the gold color to run past the back of the neck for instance.
Here is the standard on color placement:
"
The blue extends over the body from back of neck to root of tail. Hair on tail is a darker blue, especially at end of tail.
Headfall
A rich golden tan, deeper in color at sides of head, at ear roots and on the muzzle, with ears a deep rich tan. Tan color should not extend down on back of neck.
Chest and Legs
A bright, rich tan, not extending above the elbow on the forelegs nor above the stifle on the hind legs. "
Also look at the father -- he has just as much to do with this as the mother.
I probably would pass on the puppies, if the mother does not have the proper color placement. Just a lighter silverish blue would not deter me, but if color runs then I would probably look at another litter. I would not go for an all gold parent or other color deviations. But that is because I was specifically looking for a yorkie -- one that meets the standards. I wanted the potential to breed, even though I am still a ways off from the decision. I would also only make a decision in person.