The best age to differentiate sable from brindle is between 24 and 48 hours after birth. At this time, the colours have had time to develop, but the coat is still short enough to distinguish between the two.
A true brindle coat will appear mottled, blotchy, or striped, with two or three different colours throughout the coat, and the irregular pattern is distributed throughout the entire coat. In a sable coat, there is an even distribution of dark hairs sprinkled through the coat, often with a concentration of darker hair along the back, legs and facial mask. For more information and photos of Sable or Brindle, please see their individual pages.
Sometimes differences between a sable puppy and a brindle puppy are quite obvious and othertimes they are much more subtle as you can see from the photos below.