The ceres of budgies are strongly influenced by their hormones.
My mother currently has about 150 breeding budgies, and they have all different colour ceres. (as in shades - the type/colour also affects the cere shade.) (Mum breeds a mix of mutations, Aust Pied, Danish Pied, Cinnamon, etc.) Yours appears to be an Aust Pied, not sure about cinnamon at that angle?
I may be wrong, because an out of condition bird is harder to sex than one in condition - but I think this is an out of condition male.
Letting the 2 birds interact will help to make something happen if I am wrong.
Mum has 25 pairs in the breeding cabinets at the moment, but this particularly cold winter is dampening their enthusiasm.
If you were nearby I would suggest letting her do a pelvic test for you. Experienced breeders know how to feel the pelvic bones carefully to tell the gender of an in condition bird, this is also less effective when not in condition. But works pretty good if they are "coming up" into condition as an early indicator. Before the cere changes.