Aside from Jamie and Claire’s wedding clothes, there is no other costume straight from the book that I’d like to see. Except for this one, in Dragonfly in Amber. There have been hints that it will feature - and I think it will be absolutely stunning.

I closed the door of the drawing room quietly behind me and stood still a moment, gathering courage. I essayed a restorative deep breath, but the tightness of the whalebone corseting made it come out as a strangled gasp.
Jamie, immersed in a handful of shipping orders, glanced up at the sound and froze, eyes wide. His mouth opened, but he made no sound.
“How do you like it?” Handling the train a bit gingerly, I stepped down into the room, swaying gently as the seamstress had instructed, to show off the filmy gussets of silk plisse let into the overskirt.
Jamie shut his mouth and blinked several times.
“It's… ah… red, isn’t it?” he observed.
“Rather.” Sang-du-Christ , to be exact. Christ’s blood, the most fashionable color of the season, or so I had been given to understand.
“Not every woman could wear it, Madame,” the seamstress had declared, speech unhampered by a mouthful of pins. “But you, with that skin! Mother of God, you’ll have men crawling under your skirt all night!”
“If one tries, I’ll stamp on his fingers,” I said. That, after all, was not at all the intended effect.
But I did mean to be visible…Judging from the stunned look on his face now, I had made a good beginning. I sashayed a bit, making the huge overskirt swing like a bell.
“Not bad, is it?” I asked. “Very visible, at any rate.”
He found his voice at last.
“Visible?” he croaked. “Visible? God, I can see every inch of ye, down to the third rib!”
I peered downward.
“No, you can’t. That isn’t me under the lace, it’s a lining of white charmeuse.”
“Aye well, it looks like you!” He came closer, bending to inspect the bodice of the dress. He peered into my cleavage.
“Christ, I can see down to your navel! Surely ye dinna mean to go out in public like that!”
I bristled a bit at this…Jamie’s reaction was making me feel defensive, and thus rebellious.
“You told me to be visible,” I reminded him. “And this is absolutely nothing, compared to the latest Court fashions. Believe me, I shall be modesty personified, in comparison with Madame de Pérignon and the Duchesse de Rouen.” I put my hands on my hips and surveyed him coldly. “Or do you want me to appear at Court in my green velvet?”
Jamie averted his eyes from my décolletage and tightened his lips.
“Mphm,” he said, looking as Scotch as possible.
Trying to be conciliatory, I came closer and laid a hand on his arm.
“Come now,” I said. “You’ve been at Court before; surely you know what ladies dress like. You know this isn’t terribly extreme by those standards.”
He glanced down at me and smiled, a trifle shamefaced.
“Aye,” he said. “Aye, that’s true. It’s only… well, you’re my wife, Sassenach. I dinna want other men to look at you the way I’ve looked at those ladies.”
I laughed and put my hands behind his neck, pulling him down to kiss me. 
…“Lord, woman, have ye no notion what ye look like in that gown? It makes me want to commit rape on the spot. And these damned frog-eaters havena got my restraint.” He frowned slightly. “You couldna… cover it up at bit at the top?” He waved a large hand vaguely in the direction of his own lace jabot, secured with a ruby stickpin. “A… ruffle or something? A handkerchief?”
“Men,” I told him, “have no notion of fashion. But not to worry. The seamstress says that's what the fan is for.” I flipped the matching lace-trimmed fan open with a gesture that had taken fifteen minutes’ practice to perfect, and fluttered it enticingly over my bosom.
Jamie blinked meditatively at this performance, then turned to take my cloak from the wardrobe.
“Do me the one favor, Sassenach,” he said, draping the heavy velvet over my shoulders. “Take a larger fan.”