It can be a challenge, but I prefer to think of it as a puzzle to put together. I start with a fabric I love, then audition tone on tones and one or two of varying scale and contrast. I change my mind a lot and don't settle till I feel peace and joy. With the pattern you have linked to, I'd definitely mix up a number of prints, especially for a baby quilt where visual stimulation turns it into a toy, not just a quilt. If you're not confident, you could shop from a particular collection where the colors coordinate and prints are varied in scale already.