There are not many pups in a litter that I can track from birth, however Olive I can. When she was tiny she had a very fawn head and black muzzle, While cleaning up photo files today I easily picked her out. Here is a little photo journey of Olive from birth to present.
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Only a couple hours old Olive's fawn head really stands out.
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A few days old
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2.5 weeks old
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4 weeks old
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8.5 weeks old
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5 months old, the fawn has almost disappeared and her beard is no longer black.
Lots of my puppy inquiries are for a 'light' pepper & salt, or a dark coat, or as dark a mask as possible. It's pretty clear from these photos that it is a bit of a crap shoot. Best I can do is ensure that the pups they get will be a grey (pepper & salt) pup :-)