Lenne's final character design was based on her Japanese voice actress' real appearance. As you can tell in her concept art, her original design was quite outrageous, making her look like more of a prima donna then she is now. Her final look is better. Her voice actress, Koda Kumi, is a pop singer, so this resemblance solidifies the influence of modern pop culture in the game.
Additionally, Lenne gives off a very different aura in the game then her real life counterpart does, despite looking similar. Lenne is seems very melancholic and lyrical, while Koda releases a sensual and audacious energy. This demonstrates how well-defined (for a minor character) Lenne was in that she conveyed a personality distinctly different from her physical muse.
Purple: This is the color I mainly associate with Lenne due to (1) the subtle purple accents in her makeup and accessories, and (2) that fmv shot against the lavender skies. It just seems to fit her, in terms of color symbolism as well. (The webmaster of Pearl agrees!) Purple is traditionlly thought of to be associated with wealth and luxury, as it was frequently used by royalty. It is elegance and sophistication. Due to its rarity in nature and difficulty in recreation, it is also thought of as mysterious, which naturally lends itself to being associated with femininity.
Blues & Whites: These are also colors I strongly associate with Lenne due to the colors in Lenne's songstress outfit and promotional images. Blues represent loyalty, woe, and serenity. Whites represents purity, innocence, and simplicity. (In many countries, white is also the color of death.) The soothing colors in Lenne's pallete serve to contrast and balance with her lover Shuyin's aggressive color pallete of red, yellow, and black.
Brown: I think that analysing the color brown is really pushing the limits of speculation. Lenne is tan and brunette because she's based on her voice actress, Koda Kumi. That's pretty much it... However, let's consider it anyway, just for fun! In a practical sense, this earthy shade adds to exoticism of her already elusive persona. Quite frankly, animation, film, and video games need more variation in skintone anyway, so I'm glad that little coincidence worked out. Futhermore, brown is a natural color that invokes sensibility, security, and reliability.
Lenne's figure creates a silhouette that you've seen before on Japanese sailor girl school uniforms, magical girl costumes, and jpop idol fashion. It's the fluffly skirt, and the flowy fabrics, and ruffled trimmings. It's a figure that embodies the image of youth.
At first glance, it doesn't seem that Lenne, a mature and elegant figure, has much in common with other figure who sport the same silhouette, with the exception of music singers. Aside from the connection with her voice actress, perhaps we can see this allusion to youth as reminder of Lenne's tragedy. In the past, Lenne was a young lover with a seemingly promising future. Then the battle between Zanarkand and Bevelle robbed the youth of both nations of their lives and potential, as most senseless wars often do.