The vast majority of the time a hen will accept and raise anything she hatches, ducks, turkey, pheasant, even those weird looking decorative chicks. But occasionally you get one that won’t. Different people have experienced different things with this but I’ll recount two of mine.
I had a hen that hatched eight chicks a couple of days earlier than she was supposed to. I was off visiting my granddaughter so I was away, didn’t get back until the following day. That happens a fair amount of the time, them hatching early or late, not exactly at 21 days. Anyway, the young lady taking care of them called me and said the broody hen was killing her babies. I told her there wasn’t anything she could do because it would have been too difficult for her to do what was required and she was a college student. She had other things to do and did not know where things were. It was rough on her and me. Lesson learned, be home when they hatch. When I got home the hen had killed three chicks. The chicks were different colors but that did not play a part, the ones she killed were different colors and the ones she didn’t kill were also the same different colors. But when I got home she was taking care of the other five and she raised them fine. I have no idea why she selected those three.
Another time I had a broody hatch two red chicks (also a bit early) but I also had a bunch of eggs in the incubator that hatched a couple of days later although they were started at the same time. The ones in the incubator were red and black. That hen spent a couple of days with her red chicks and bonded to them. When I gave her the incubator chicks she accepted the red ones fine but rejected the black ones. I had to raise those myself. I’m convinced color made the difference that time. This was her second hatch that year. Earlier that year she hatched and raised red, black, and yellow chicks. It was bonding with those red chicks this time that made the difference.
There are different theories about why a hen might reject some chicks and accept others. I don’t know what triggers that killer instinct in some. With living animals you can’t know why for sure all the time. Watch her and see if you need to intervene with any other chicks. She might raise them fine, she might not.
With that chick, keep it warm and let it rest. You could try getting some electrolytes and mixing those with water. I’ve used plain sugar before, just something to rise its energy level. Put a drop of that water on the tip of its beak. It will probably swallow it. Do not put water down its throat, you’ll drown it. Just a drop on the tip of the beak should work.