1. The Gray Dress: Work
Try charcoal instead of black—less stark, but just as good a mixer.
"Clean lines, good construction, not too trendy—this dress is so my style," says interior decorator Erica Obert-Male, 41, of the long-sleeved wool sheath (Ellen Tracy, $398). What gives it pizzazz: adding some color. It's important to look coordinated in the office, so the belt (Hobo International), bag (The Jack Rabbit Collection), and pumps (Nine West) are all a similar shade of wine. Gold-tone jewelry (necklace, Isabel Harvey; watch, Longines) adds warmth and class.
2. The Gray Dress: Evening
Powerful by day, seductive by night, this sleeveless stretch crepe dress (Jones New York, $150) is the perfect office-to-dinner piece. Go to work wearing a jacket for coverage; take it off when the day ends, showcasing a richly beaded neckline. Switching to accessories with a little glitter doesn't hurt, either—even the tights are shimmery (DKNY Hosiery).
Earrings, House of Lavande. Ring, Alexis Bittar. Clutch, Judith Leiber. Shoes, Jimmy Choo.
3. The Gray Dress: Weekend
Looser schedule? Go for less-structured clothes and experiment with pattern mixing. The striped cardigan (Rare Woman, $254), paisley scarf (Me & Kashmiere), and plaid tote (Burberry) incorporate a bunch of colors—not only the gray of the easy-fitting smock dress (Tribute, $218) but pink, purple, caramel, and wine. Neutral accessories (belt, Linea Pelle Collection; boots, J.Crew) anchor the prints.
Pendant, Jenny Bird. Ring, Jessica Robinson Jewelry. Tights, DKNY Hosiery.
4. The Gray Dress: Get it for Less
Avon, $30; 800-367-2866 for an Avon Representative
5. The Tan Trench: Work
Svelte enough to be sexy, roomy enough to go over layers.
Secret agent mystique in a practical package—that's the beauty of this coat (London Fog, $100). Here it's paired with the season's "it" color: purple. "I love that deep, regal shade," says Denise Hungerford, 41, a marketer for an entertainment company. Her sleek ensemble: tweed suit (Talbots jacket, $219, and skirt, $119), shirt (DKNY Jeans, $79), and suede shoes (Ron Donovan).
Earrings, Wendy Mink Jewelry. Ring, Wendy Brandes.
6. The Tan Trench: Evening
Take a frothy skirt (Repetto, $128) and rosette-trimmed top (Sportmax, $115) and adopt the habit of flinging a trench (Martin + Osa, $170) over evening clothes for a nonchalant mix. This coat's lustrous fabric is dressy-looking and supple: "I'm learning to extend the trench's range by playing with it," Denise says—wrapping, belting, tweaking the collar and sleeves. A creamy palette keeps the outfit unified.
Earrings, ABS by Allen Schwartz Jewelry. Shoes, Pedro García.
7. The Tan Trench: Weekend
Riding the menswear trend, the trench (Tommy Hilfiger, $228) hangs out with a checked jacket (Liz Claiborne New York, $159), crisp shirt (Club Monaco, $69), and skinny corduroys (Gap, $55). The big, slouchy chain bag (Anya Hindmarch) and ballerinas (Kate Spade New York) are just the ticket for dashing around doing errands: "Nine times out of ten I'm in flats," Denise says. "I can't let heels slow me down!"
Hoops, Sequin. Bangles, Kara by Kara Ross.
8. The Tan Trench: Get it for Less
Old Navy, $50; 800-653-6289
9. The Navy Blazer: Work
For maximum flattery, look for a slightly shaped, unboxy jacket.
As authoritative and fail-safe as a matched suit, but fresher: A navy jacket (Esprit, $160)—in a seasonless cotton blend—and gray flannel pants (Express, $80) are great for a financial professional like Joy Booker, 38, who works at an investment-management firm. But a witty surprise—a top striped like a man's tie (Kate Spade New York, $225)—is not against corporate rules.
Belt, The Jack Rabbit Collection. Ring, Kenneth Jay Lane. Shoes, Furla.
10. The Navy Blazer: Evening
Masculine meets feminine when a curvy blazer (The Limited, $158) steps out with a tie-front sequined top and lace skirt (J.Crew, $495 and $850). Joy is intrigued by the jacket's ruched sleeves, which look as if she just pushed them up: "It's a very 'designer' cut for a reasonable price." Gray and silver accessories (clutch, Hype Handbags; bracelets, Tejani; shoes, Sergio Rossi) go well with navy because they're in the same cool color family.
11. The Navy Blazer: Weekend
Once this cropped, gold-buttoned blazer (J.Crew, $178) leaves the office, it should be treated casually, like a jean jacket. Here it's tossed over a turtleneck (J.Crew, $158) and striped button-down (Brooks Brothers, $90). Turn the shirt collar up so the points peek out; it's a cool way to layer. White jeans (Tory Burch, $175) are fabulous year-round—don't put them away after Labor Day.
Earrings, Kevia. Belt, CC Skye. Shoes, Lauren by Ralph Lauren.
12. The Navy Blazer: Get it for Less
Blazer, George, $22, Walmart; 800-925-6278 for stores
13. The Black Skirt: Work
Pick a realistic style for your body with ease where you need it.
Flaring pleats near the hem give this skirt (Worthington by JCPenney, $36) a graceful shape that balances hips. "For me, black trumps other neutrals," says Organizing for America volunteer Weez Tomlinson, 50. "I love its allure." Not to mention how good it looks with elements as soft and colorful as a velvet blazer (Anne Klein New York, $395) and ruffled shirt (Ellavie, $69).
Earrings, House of Lavande. Bag, Banana Republic. Tights, Donna Karan Hosiery. Shoes, BCBGirls.
14. The Black Skirt: Evening
Weez's favorite skirt shape is the pencil because it's so slimming and elegant. Besides, she's a fan of clothes that "go easily from day to evening," and this sexy, side-slit style (Victoria's Secret Catalogue, $59) certainly qualifies. A glamorous double-breasted silk taffeta top with puff sleeves (Rickie Freeman for Teri Jon, $320) makes these separates as party-worthy as a drop-dead dress.
Earrings, Roberta Chiarella. Bracelet, Iman Global Chic. Ring, Kenneth Jay Lane. Shoes, Valentino.
15. The Black Skirt: Weekend
A roomy skirt that doesn't look sloppy (Thrive, $350) is fabulous for Saturdays...or anytime. Add layers so you can pile on or peel off as the weather evolves (it's nice to work in some brown—more casual than black): This striped shirt (Jones New York Signature, $69) is topped by a bicolored cardigan (Christopher Fischer, $198) and metallic lambskin jacket (Lafayette 148 New York, $898).
Boots, Kenneth Cole.
16. The Black Skirt: Get it for Less
Lane Bryant, $50; LaneBryant.comMore from O's Fall Fashion Handbook