This is a so-called Clicker ring with a small hinge sitting in one part of the segment, which makes it very easy to open and close.
Roseline® is gold colored jewelry, they are not "colored" in the classic sense, it is 316L Steel or Titanium that is covered with a thin plasma film (PVD coating). The thin film is very strong and does not fade. The technology has been used since the late 80's and is used, among other things, for orthopedic implants to provide an extra durable surface.