My personal Josephine's aesthetic headcanons
If I were to do a more complex character and costume design for Josephine, maybe for a live-action movie, I would picture her as having a rectangular bodyshape, because it would help mirroring her evolution, social standing and relationship with her environment at best when it goes down to costume design.
Pre-revolutionary fashion was an era based on the contrast between the narrowness of the waist and the great volume around the sides and legs. The stays were triangular in shape sinching at the waist. No matter the adjustments to guarantee comfort, this style wasn't flattering for someone without a naturally defined waist.
On the contrary, Empire fashion's distinctive feature was the lack of definition of the natural waist, focusing instead on creating a vertical line and a uniform figure. It is the most flattering style for people with rectangular bodyshapes.
Josephine in her first years in France as Beauharnais' wife felt out of place and insecure about fitting, while during the Empire she was literally the leader of fashion. No matter how elegant and pretty she would be, her French outfits before the Revolution would look uncomfortable and not flattering on her, while her Empire outfits would be the perfect fit and style for her.
When it comes to armochromic seasons, I deem her a Autumn Deep. In pictures she is defined by a strinking chromatic contrast on her features (very dark hair and eyes) but she also looks good in warm and earthy tones and rocks gold much better than silver.
Finally, essence-wise, she was predominantly a romantic girl thoughout her lofe. She loved light and soft fabrics such as muslin, silk and cachemire and also favoured light and feminine colors. In her years as a widow and wife of a general, she mixed this romantic energy with elegant notes, while as she assumed institutional roles she declined it in a more classic way.