Sex can normally be determined at four months old by observing the ceres colour.The cere of young males is normally pinkish/purplish blue while the adult is bright blue.Young females have blueish white ceres,changing to brown when adults.Some females retain a light blue tinge that may crust and turn brown during the breeding season.
I hope the pictures of these varieties will help you overcome any difficulty when sexing your birds.

A hen in breeding condition - This hen is four months old - 12week old hen.
note the nut brown cere. - he cere is a washy blue.- Note the white nares.

ten month old ten week old eight week old
light green cock. op spangle grey cock. op cinn spangle grey cock.
six weeks old - sixteen weeks old
dom sky blue pied - lutino cock
THIS PAGE IS UNDER CONSTRUCTION - ADDITIONAL PICTURES WILL FOLLOW.