She lays four or five bright glossy blue eggs which are lightly spotted with black or purple . She lays four or five bright glossy blue eggs which are lightly spotted with black or purple ; they are typically 2.7 x 2.0 centimetres ( 0.79 x 1.06 in ) in size and weigh 6.0 grammes ( 0.21 oz ) , of which 6 % is shell .