In his opera cycle, der ring des nibelungen, wagner uses recurring themes called to describe characters and ideas.

In Wagner's ring cycle, he uses leitmotifs  as a way to remind us the important aspects about the characters besides describing them. He makes very little changes to keep us within the same line.

Let's remember that a leitmotif is a German term which could mean "a motive that guides" and it is not only used in opera, but also in other types of arts such as painting or music and these could be colors, symbols, phrases, etc. In this case, within the opera, you can clearly identify them because they are used in a very recurrent way