Because "ingenue" isn't a word that's widely used in common parlance, I've searched for other words that seemed to have meanings closest to "ingenue" as I define it in my style system. One word that worked well is "vernal" -- i.e., "springlike."
There's a lot of overlap between the Ingenue style identity and spring, both as a season of the year and as a color palette.
Light Spring in particular (a.k.a. Early Spring, significantly) is known for colors that also are iconic to Ingenue: very lights yellows, pinks, oranges, purples, and blues. Candy colors, you could call them.
Ingenue lines are fine and thin, never thick or coarse. Ingenue fabrics are light, not heavy.
Ingenue beauty is (feminine) childlike beauty. The small, round circles one sees in Ingenue style reflect a child's round eyes. An Ingenue finish in makeup is often a dewy finish -- that echoes the dewy eyes of a child, and also dew on flower petals in the morning. (Morning is to a day as spring is to a year and childhood is to a life, of course.)
Ingenue style has a quality of innocence or naivete. Can we reclaim that so that it's a positive concept and not a negative one? After all, innocence includes sincerity, which is certainly virtuous.
Ingenue patterns are simple, not difficult to comprehend (as Ethereal patterns might be.) Ingenue motifs are earnest, not witty or sarcastic (as Gamine motifs might be.) Ingenue innocence ought to be celebrated, not denigrated.
"Pure" yields a lot of associated words that are useful for Ingenues. An Ingenue look is certainly clean; dirt on the knees of one's pants could look apropos on a Natural, but not an an Ingenue. (Is that why I, as a Natural blend, feel particularly pretty when I've been working in the yard? Hmm.)
And discussing the word "pure" brings us to this idea of the Ingenue as "virginal." Whoa! Let's get into that.
Despite the fact that "virgin" is a fraught concept, I do think it's important to emphasize that Ingenue's feminine beauty is "virginal," not sexy.
I don't want to reinforce the outdated idea that women should be defined by their virginity or lack thereof.
But perhaps we can agree that there's a kind of feminine beauty that includes an erotic quality, and a kind that does not...? The first one is Romantic; the second one is Ingenue.
If you can see that a style element is traditionally feminine, but you're not sure whether it's Ingenue or Romantic, this difference ^ can help you decide.