Sorry you can't tell with Fantails.
There is a pied phase and black phase but males and females look the same.
Pied phase has grey head, white eyebrow, brown back, yellow underparts with white and black bands across chest, black and white tail. Juveniles look a bit different from adults. Browner body, rusty-brown wing coverts, and indistinct chest markings.
Black phase (mainly in South Is.) is all sooty black except white sport behind eye.