females have white ceres or white with a light blue ring on it. I believe when they get into condition it turns tan. Boys will be blue all over the cere. I think even if its a light blue if it covers the whole cere it is a boy. The photo you provided looks more of a light purple all over the cere thats why i thought male, but if you say its tan then it just may be a girl. I would try to post a better picture. I hope cutelittlebirdies chimes in for she is the expert, not I. Anyways your bird is beautiful
Mature, adult females that are not in breeding condition will have a whitish/light blue cere with white around the nostrils. Adult females that are in breeding condition will have tan to crusty brown ceres.
This applies to every color mutation.
Mature adult males have a even coverage of navy blue over the cere that becomes even more saturated in color when in breeding condition.
The exception to this is if your male is recessive pied (like Tweety), Ino, lacewing, etc. In that case, an adult male will keep his immature looking pink/purple cere. It will never turn blue.