Well, sometimes when collecting eggs, they can get mixed up if someone is not all that careful. It's a human mistake, but I happen to know the cost of their birds and eggs and you should get what you pay for or compensation for mistakes. Let's see how the chick develops and what it turns out to be. I'm not sure what would be yellow other than a white bird. Splash is usually a silvery-pearly color when they hatch, maybe with a yellowish tinge, plain splash, that is. I've had BBS Orps, BBS Ameraucanas and BBS Rocks.
I know that when folks see my photos and they come here, they see the same pens/buildings as in my photos, nothing is a shock. Not so with others with slick websites, just saying.