It looks to me like the rooster has rustiness in the neck hackles, not chocolate. That's from red in the hackles. If the rooster had a chocolate gene, it would not be only in the hackles, it would be any location that would have been black. As blue as the rest of the body is, that says to me that he is blue. The neck hackles color is just other genes coloring it up.
The hen being white and OEGB, that does give a possibility that she was hiding dun. Any idea what color her parents are??
Crossing the white (IF she was dun something under the white) to a blue, chicks could be blue, dun (single dose of dun makes them dark chocolate color), black plus any patterns or other modifiers. You'll know more when it feathers out. Chick down can be very decieving. Dark chocolate "Looking" chick down can be a whole lot of other colors too which is different than being genetically chocolate. Be sure to post more photo's later. The lighting in the last photo is pretty bad so it's hard to call that one. Take it our in the daylight, not direct sun, and get another picture. Looks a little too red to me to be dun.
Middle photo is definitely a blue chick.