In this case it's a tension ring, because it does add tension to make the crystal fit and stay in place properly. Not all crystals that look like this and have a metal ring, have a proper tension ring. Some metal rings are called a "reflector ring" that adds no tension to the crystal fit.
And yes, in trade speak anything silver is "white" and anything yellow gold is "yellow". Tension rings, crowns, etc. all use this, and certainly not specific to Omega.
Cheers, Al