In the bottle Julep looks quite a bit redder and less of the purple when actually placed side by side. When swatched, well, yes. They are still very different. So once more, similar but certainly very different.
In normal light they look very very similar, but in hte sunlight as you can see, Dior Black Plum is much more purple and probably a good 3 shades darker. Julep Keira is more of a true berry, a purpled out burgandy, where as Dior is a darkened, berried plum. Both colours are gorgeous, just very different!