IB, or any color for that matter, can and usually do show a sign of split blackshoulder. The forward shoulder area will be partially black and iridescent.I think , if you cross PURE line of Blue and PURE line of Blue BS the first generation will be Blue .... the phenotype will be totally Blue like a pure blue peafowl . Spots of green on the wings are often coming from mix blood or spalding ascendants .There is no outward sign for the Blue peacocks split BS.