Curis marmorata is that purple coloring babies get when they are cold or upset. As the skin matures it does go away. CMTC is a vascular birthmark that doesn't go away. It may lighten some as your child matures but may not. It is always present even though at times it may be lighter. It darkens when cold or your baby is stressed (sometimes warm also). It may have other health issues but not always. I am in contact with families that have children with only markings and some with many health issues. Doctors can't predict if your child will or will not have further complications.
I forgot to mention I am a mom of a three year old with CMTC.