A fairly easy species to sex visually. The cock (left) has a slightly larger head, with a thicker, stubbier bill. The hen's is more pointed and slender.

 

Also evedent when viewed from above, cock's bill more thick-set with a wider crown (left)

 
Yes Amit juvis will also be grey-ish. Its always been the Magpie Mannikin, at some point the slang name "pied" surfaced and it stuck to the point that even some books call it that.