You can look at their vents. The hens have an open void and usually poop on you if you mess with them. The males have a bulbous gland and if you press on it, foam comes out.
Beer Sex Them.... Grab A Beer And A Lawn Chair, Some Zip Ties, Maybe A Sandwich Or Chips....
If It Crows Its A Roo, If It Lays An Egg Its A Hen, If It Mounts Other Birds Its A Roo... Now Here's The Catch... If It Gets Mounted It Could Be A Hen Or An Unfortunate Lesser Ranked Roo.
I have had tuxedo pied button quail for a couple of years. I have noticed on the males, if the color comes down far enough, there is red on the rear underside of the bird. Have got mine in trios, so far so good.