Although this example is not marked, it is from 2005. The original Opaline Yellow was a warmer color; Yellow is on the cool side with an undertone of green. This example is also cased. A yellow color called Opaline Yellow was reintroduced in 2000. However, in the 2001 catalog the name was changed to Yellow, because there was very little opaline showing up in the glass. Yellow has been made each year since including 2012 although not always as a catalog color. This is the same yellow color used to make Fire and Ice pieces.
Opaline Yellow on the left and Yellow on the right.