Quoting "The Beginner's Guide To Ringneck Parakeets" by Theresa Jordan
Ringneck parakeets are sexually dimorphic, usually at two to three years of age--meaning that the sex of a Ringneck can be determined by its coloring. Sometimes sex cannot be identified until the bird reaches this age due to the time it takes for younger birds to show their final coloring. In appearance, they are exceptionally striking birds, with the males having a more dominant neck ring than that sported by the female.
Pairing of a lutino with a blue results in the breath-taking albino mutation Ringneck. Albinism is caused by the blocking of both melanin deposits and carotenoid conversion of lipochromes, resulting in this particular mutation lacking any color pigment. Thus, they have no neck collar, making both sexes appear identical. They have red beaks and eyes, and their feather coloring is a pure, stark white. Their total lack of pigmentation actually makes these birds quite visually attractive.
