Voyager’s bright blue medical gowns are my favorite Federation medical gowns by far but they are standard issue (and no one looks better in them than Seska).
And this purple sheet is just not an outfit. It is the absence of clothing.
In this case there is a perfectly reasonable, and in fact wonderful, reason for Kes to be undressed: she’s giving birth to her daughter with Tom in one of my favorite crazy sci-fi time travel telepathy episodes that never happened (look how CUTE they are). It, and the baby’s blanket, are purple, not medic blue, but it’s a stretch to say that’s anything other than a girly color. Kes expresses her individuality in silhouette, not color.
tldr; I have nothing against either of these, just they don’t say anything interesting about Kes