As the puppy grows older, the facial wetness from nursing will cease, and the hair will gradually whiten on its own.
This is the same issue as the tear stain development in many of Papillons and other small Toy Breeds.
Constant wet fur /hair , as in tears, milk from lactating mom, breeds bacteria and what you see is the red yeast responsible for the red/ brown coloration under the eyes, or in this case face and front paws.
See also:
http://www.roadsend-papillons-phalenes.com/2012/01/tear-staining-in-papillons-and-other.html
http://www.roadsend-papillons-phalenes.com/2010/09/you-ask-tear-stains-in-papillons.html