Achdar (Blue)Bolk has a pastel or opal shield and two black bars. Their beaks tends to be slightly longer than the rest of Bolks.
They are among the smartest and the strongest Bolks when properly selected.
On left above is a two years old male followed by another male. Below are two two youngsters from the same nest at two months. The blue mark on the chest of the top bird doesn't usually reflect on the offspring's as noted on the two youngesters below.