This drink dates back to the late 1800s and there are a few versions of this cocktail. Many specify the use of Crème Yvette or blue orange liqueur. The problem with Crème Yvette is it’s red not blue. So that doesn’t work. Although it’s understandable people would use Crème Yvette as it is similar-ish in taste to Creme de Violette but it looks completely different. Second from everything I have been able to find it looks like blue orange liqueur was a later substitute for Creme de Violette, as Creme de Violette was not sold in the United States from 1919 to 2007 and they both share a blue color. As far as taste goes think of this as a Dry Martini with a blue liqueur added to give it the schools color and add a little sweetness.