Hi there and
to the forums!
You've been given great advice so far on Bubo's condition and I truly hope that you'll be able to get a diagnosis from the avian vet.
Was Bubo's cere a different colour when you first got him? Do you have a picture of how it was before? If before, his cere was pinkish or purplish that turned dark blue before the discoloration, then he really is male and this could be hormonal or possibly testicular cancer. If Bubo's cere has always been pale whitish, then he really is a girl.
Either way, I reckon a vet visit is in order, which will help to clear up any doubts about what is causing the discoloration.
Please keep us posted on how little Bubo does! I really hope he/she gets better soon
In the meantime, be sure to review the links provided to ensure you're up to date on the best forum practices.
Feel free to ask any questions you may have after reading through everything!
Best of luck with your little one!