Chickens vary in their response to threats, individually. Some birds will freeze on the ground, or under a bush, making them easy prey for a canine. Other birds will fly up into a tree (if they can) which is a fail if the hunter is a raptor. Over the years, once we have a very safe coop for overnight, losses do occur when they are free ranging. Younger smaller birds, and bantams, are easier for a raptor, and here the color doesn't matter. Our losses to a fox, once, during the day, were mature standard laying hens. I swear this fox selected hens actively laying, must have liked the eggs?!
Two of our rescue dogs killed some birds, any size, any color, and got the birds who didn't decide to fly up high in time.
We don't seem to have bobcats or bears, fortunately, and our resident coyotes have stayed away for the coop, near our house, the neighbor's, and our dog fence.
When we do have a raptor visitation, our birds are locked in for two weeks or more, until it's likely the the bird has moved on. Our coop and secure roofed run are large enough for the birds to be okay with being in for weeks, when it's necessary. Plan for a safe space that works for your flock!
Mary