The play is being staged by the Carey Players in North Carolina so the costume designer contacted Spoonflower (also located in North Carolina) to see if a Spoonflorian could come up with a suitable design.
I contacted the costume designer seeking more info on the character and the dress and this is part of his reply:
The dress is for the number called "The Paris Original Dress." In summation, one of the characters (Rosemary, the female romantic lead) thinks she has bought a new and original design for a cocktail dress straight off the boat from Gay Paree. Alas, she is mistaken, as when she arrives at the party she sees that the other women (some chorus and one or two second lead characters) all have the exact same dress.
The costume designer also gave me the details of the Butterick pattern (Retro Butterick B4790) that the costumers will be using to create the dress. Having this knowledge completly changed my approach to the design.
Retro Butterick B4790 dress pattern
Flower patterned (blue, white and brown) cocktail outfit with full, gathered skirt and matching blouse with scoop neck and Peter Pan collar and five buttons down the front and capped sleeves. An alternative sleeveless gold blouse has a scoop neckline with a drape across the bust going up over the neckline. Spring 1960.
From the London College of Fashion Victor Stiebel Archive
hope you like it!