I'm no scientist, but I've read and heard that babies enjoy the high contrast of black against white. So I've made quite a few quilts that are black and white with a selected color, for this reason and the following...
I truely hate picking out fabrics for quilting... I spend hours wandering around the fabric store, picking things up, carrying them around, finding something else I like better, then trying to figure out where I got the original item from so that I can put it back. I'm sure the people working there hate this, but also I've been assured that it is relatively common. Also, having worked in a fabric store I feel like I've done my time doing the clean-up :)
Using B/W fabrics generally solves this issue for me... B/W fabrics nearly always match, and it's easy to incorporate just a bit of color, rather than worrying about color schemes, shades, etc.
The following baby quilt was relatively easy to lay out, and I'm posting it to celebrate the 3rd birthday of the little one for whom it was quilted. I cut 5" squares out of each of the selected fabrics, put one in the middle of the floor, and then built out from there making a symetrical yet not too obvious pattern.