I don't see any brown... is that a wheaten?
But for a wheaten, whether it is blue wheaten or splash wheaten, the brown on the breast will be the same as regular wheaten (remember that BBS is only working on the black coloring).
So, if it is a wheaten, just look at the breast feathers. As...
I don't have blue wheaten.. just wheaten, but here are a Male and a female, not much older than yours...
The male is already pinking up on his comb, and of course all of those dark feathers.
Girl is all.... well... girl wheaten color.
Female left
female left
female left
Female
Male left