Now in that pic it looks much lighter, IMO it's not really dark enough to be a Brown in that pic, not even a Brown male (which will be lighter than a Brown Hen)... so now I'm guessing it's either a Pied Buff Dundotte Hen, or a Pied Cinnamon male
I have a few that look pretty close to that one, and I call them Cinnamons, but the Cinnamon in Australia is much darker, and what I consider a Brown in my flocks... and like I've mentioned before different breeders call different shades of the tan gene birds by different names (and would call that keet a Brown), so you can call it what ever you want, lol. I'd keep it too, it'll be a gorgeous bird to have in your flock - "Yard Art"
If you only have 1 Pied Hen in your flock, then that has to be who laid the eggs these keets came from (if they are all pied anyway), and she is obviously carrying a recessive tan gene. If you got a couple of these keets that aren't Pied then it's possible your other Hens may
all be carrying the tan recessive gene too, you never know, lol. Is your male an actual Buff (only partially pearled on the flanks and bars on the wing feathers like a Royal Purple or a Coral Blue) or is he a Buff Dundotte (fully pearled all over like a Pearl Grey)?