She was actually my first budgie that I had that the cere changed color! I bought her and the green one at the same time from the same breeder as adult birds... and both had crusty brown ceres. She lost half of the crustiness shortly after bringing her home. That first image also has the green hen in the same image. (you can only see the back of her neck in the cropped image!)
Males typically have pink, purple or blue ceres. I once saw a picture of a male that had a tan cere, but it was a shiny, bulbous tan color, not the same flat dull color of a hens. I've also seen males with crusty brown ceres, but this is due to a hormonal imbalance often caused by tumors.
Hens can have white, white with blue, white with tan, white with blue and tan, tan, brown, and crusty brown cere's. Some hens can even have a deep blue cere that could be mistaken as a males! And others may have a reddish hue to their brown ceres.