If the little girl is staying there occasionally, maybe the mother could ask what she would like for colors for the new baby and maybe that would be a better choice of colors. Don't worry about the black and gray so much. Babies tend to like the black prints. My daughter has a mobile all in black designs which was a big rage and some kind of psychological thing back in the late 90's. I know that all three of my grandchildren were totally mesmerized with that mobile. So go find some black and white print with some good designs on it. But I am really like most of the other people on this board. I never ask, I just present.