While it's more common for male budgies to have a distinct blue or purple tint on their beaks, especially when they reach sexual maturity, female budgies can also exhibit a variety of beak colors, including blue, pale blue, or brownish.
The beak coloration can be influenced by the specific mutation, genetics, and age of the budgie.
For example, some female budgies of the "spangle" mutation may display blue or violet beak coloration. Additionally, as female budgies approach breeding condition, their beak color might temporarily take on a brownish hue.
To accurately identify the sex of a budgie, it is recommended to consider various factors in combination, including the bird's behavior, overall body size, head shape, and cere coloration (wax membrane above the beak), in addition to the beak color.