My supposedly male budgie's cere turned brown?

yep its a girl. they will be ready to breed soon if they are make and female. sounds like they are. put a nest box or one of those basket nests you can get from petshops in. give them a cuttlebone and add egg and biscuit mix and grit to their food. (these can be bought at a petshop) if you live in australia cj petmart is good although theres only one in hornsby.