There is a great thread on the boards all about decorating magic bands. I used a clear base and top coat nail polish as a base coat and then used acrylic paint, then the same nail polish as a top coat. No cracking or pealing. I have also used sharpies, and acrylic paint pens. Always using the base / top coat nail poilish before and after.
I did notice with my DH’s band (gray one), and the only one that I didn’t do a coat of paint first, that his paint did scrape a but from wear and tear. Mine (purple) and my DD’s didn’t have any problems at all. .Have fun!