This particular type of Sun Conure is the result of a mutation visible in some chicks born from 2 regular Sun Conures: their plumage appears entirely yellow, lightly speckled with green, while their beak, feet and claws were white.
After the first molting, this mutated conure looses the green feathers and becomes entirely yellow; with time, part of the beak darkens, but it generally stays whitish, as do the feet and claws.
As the Lutino Sun Conure reaches adulthood (18 months), its body becomes entirely yellow except for its head and belly, which are bright orange. The contrast between its darkened bill and yellow plumage makes this bird strickingly beautiful.
To learn more about its temper, see the Sun Conure description.