Why do you feel terrific one day and rotten the next? Why does one applicant beat out another--similarly qualified--person for a job? Why is a jury sympathetic to one witness and cold toward another?

Why do you have a closetful of clothes and nothing to wear?

The answer, claim proponents of the fastest-growing segment of the new image-making industry, could be color. Within the last few years, thousands of people--from therapists seeking help for depressed clients to executives bucking for promotion--have flocked to these "color psychiatrists" who claim that the proper palette can cure everything from a lean budget to a dull sex life.

"Color is magic," asserts hue guru Carole Jackson, whose book Color Me Beautiful is in its 31st printing and has hovered atop the best-seller charts for close to two years. "Artists have known for centuries that color affects you 100 percent of the time, but often at an unconscious level.

"Everyone is born with an inclination towards certain colors, but by the time we grow up we buy colors for other reasons--because gray pin-stripes are supposed to mean power or because our mothers dressed us in certain shades. Wearing the wrong colors can make you look and feel off.

"But when you wear colors that suit your individual skin and hair and eye tones, the difference is dramatic. People feel better, look better and as a result often succeed better in their personal and professional lives."

This rainbow concept has meant a pot of gold for Jackson--whose company analyzed 90,000 people and grossed more than $2.5 million last year--and for other pioneers in the exploding color industry. While 10 years ago only a handful of consultants offered color-analysis services, today nearly 6,000 people around the world have paid $150 to $2,900 for training and certification by the three major nationwide corporations:

Color Me Beautiful based in McLean; Beauty for All Seasons, Idaho Falls, Idaho; Color 1 Associates, Northwest Washington and Riverside, Calif. In addition, hundreds more have set out their own color-analyst shingles on an individual or regional basis with names like Color Concepts and Color My Image.

Although critics contend that color analysis is "a crutch" at best and a "rip off" at worst, legions of clients are paying anywhere from $35 to $75 for a color consultation: The analyst studies skin, hair and eye tones and provides a spectrum of shades to best complement natural undertones.

Both Beauty for All Seasons and Color Me Beautiful categorize clients in one of four color groups--spring, summer, winter, fall--and provide a packet of fabric swatches pre-selected for their seasonal group. (Queen Elizabeth, for example, is a "summer" according to CMB; Richard Nixon a "winter.") Color 1 consultants create an individualized "color-harmony chart."

Besides "the ego boost from looking great in your own colors," says Color 1 president JoAnne Nicholson (whose clients include Rep. Bill Frenzel (R-Minn.) and the Beach Boys), "color consultation simplifies your life . . .everything you own goes with everything else, and it helps avoid costly mistakes."

Whether for vanity or economy, "The color rage is not a fad--it's a trend," claims Amelia Myers of JCPenny Co., which has sponsored color training for employes in about 18 cities. "More and more customers are coming into the stores with their color swatches, and we wanted our sales staff to be able to help them."

Other stores, such as Neiman- Marcus, have trained their sales staffs in color analysis; some have set up in-store boutiques based on the concepts. Amway and Mary Kay Cosmetics are promoting the idea in home sales. Savvy manufacturers of everything from cosmetics to eyeglasses are gearing new products to the color wave.

Men, says Roger Raley, an Olney Color Me Beautiful consultant and hair-salon owner, account for about 30 percent of the "hundred or so" color analyses he does each month. "They've seen the great things it does for women, and figure it can work for them, too."

"The dress-for-success rules--like wearing blue to open a deal and wearing black to close it--don't work for all men," maintains Raley. "If they've got reddish-brown hair and peach-toned skin the sharp black and white contrast can make them look sick. They can get the same power effect, and look great with a dark chocolate suit, oyster white shirt and coffee-colored tie."

To attract this male market, which now accounts for "nearly 40 percent" of Color Me Beautiful's business, Jackson is coming out with a new book--tentatively titled Color Me Handsome.

Interest is also growing among professionals "to enhance their own services," says Victoria Eubanks, a Washington area Beauty for All Seasons consultant.

"Lawyers use it to help their clients give the right image . . . Entire corporations are having their staffs analyzed so they're more effective in areas like sales and dealing with the public."

"Therapists through the years have told their depressed clients to go out and get a red shirt," says psychotherapist Elaine Weiner who integrated color consulting into her Silver Spring practice last year. "The new external image supports the internal changes."

A former model in practice 31 years, Weiner charges her patients--and those referred by other therapists--$75 for color and wardrobe consulation. "I went shopping with one young woman lawyer who had been depressed. We completely redid her colors and wardrobe. It changed her life."

There are those, however, who believe the trend should be viewed with a certain skepticism.

"Obviously color is a key element," says fashion designer Diane Von Furstenberg, "but the rigidity of telling people they can only wear certain colors is ridiculous. You're not necessarily the same woman from day to night, from Monday to Saturday and all your life. I never like any type of slavery."

Even though one color consultant told her she was a "winter" and another that she was a "definite autumn," Alexandria research specialist Marsha Thole still found the consultations "worthwhile . . . a good, helpful tool.

"The trouble is, people are believing this as if it were God's truth. They won't look at any other color than the ones their analyst chooses because they're scared to death they won't look right.

"If Carole Jackson were to die tomorrow they'd be paralyzed and unable to get dressed."