I ove this cocktail but this time tried as per suggestion of others of adding some rich simple syrup. For me 2.5ml / .5 tsp struck a great balance with the lemon. I wonder though if one uses the optional sugar rim if that would negate the need for the syrup. Will try this next time. (As an aside, for those looking for the lovely light blue hue of the sky, I can't recommend Bitter Truth's Crème de Violette highly enough!)
Tried this tonight and this is a delicious cocktail. As per Tapan Patel's suggestion of adding a little lemon, I added only a few drops and can attest that this really brightens the drink. For those curious as to who "RIP" the author of Cocktails de Paris was, it was the nom de plume of Georges Gabriel Thenon, a singer and author of revues from the early 20th century. The book was illustrated by Paul Colin, one of France's great poster artists. (Another great cocktail from that book, is the "Cocktail de Paris": https://www.diffordsguide.com/cocktails/recipe/35044/cocktail-de-paris )
Brilliant suggestion; tried as per recipe and after a few sips squeezed a few drops of lemon juice into my glass just to compare. Even that small amount brightens the drink and cuts down a bit on what some might find a bit of cloying cocktail from the Yellow Chartreuse.