Fresh, no-fuss clothes with a touch of fun

Teachers accustomed to a sea of faded-blue denim in classrooms are sure to blink when students come trooping back to school this fall in a glorious blaze of color. Purple, coral, turquoise, burgundy, fuchsia, rose-red - all are in sharp contrast to color choices available in recent years.

How did children's-wear designers manage this turnaround? How did they coax kids out of the blue-jean mold, even temporarily? By giving them fresh, no-fuss clothes with a touch of fun. By letting them experiment with a whole new range of colors and discover untapped beauty.

Purple is the big surprise. Never considered a young color (maybe royal happenings in England played a part here), an electric purple seems to have captured young imaginations. It's turning up in action wear (fleece sweatshirts and pants), corduroy jumpsuits and overalls, fiber-filled nylon jackets, velvet skirts, and plaid blouses, all for girls sizes 7-14.

One style for girls already proven magnetic is the 1982 version of the miniskirt, designed to be worn with tights. Most resemble skating costumes. Some are attached to tops, others have matching pullovers. Red-striped jersey looks newest, but the skirts are also featured in denim.

Prairie denim skirts with below-knee ruffled hems continue to be popular. Those by Gloria Vanderbilt for Murjani are cut with fitted-waist yokes, front and back. Instructions say to wash them inside out to avoid streaking.

Plaid and printed blouses from this line make a point of high ruffled necks, puffed shoulders, asymmetric closings, and side-buttoned bibs. Very pretty, they are suitable for school or dress, and often have ribbon bows at the neck. Size range is 7-14.

For preteens, loose-fitting jersey tops with ruffled peplums are eye-catching , but dolman tops in acrylic knits for teens have a distinct high-fashion look. Here again, colors are showoffs. Bands of burgundy, green, navy, and purple emphasize deep armholes and sleeve widths. Fronts and backs are in solids.

A new collection of polo shirts (long and short sleeves) for boys come in so many different hues they remind you of color charts in a paint store.

''Boys have never had such a color choice before,'' one merchandiser says, ''so this is very exciting.''

To blunt blustery days, outerwear makers are introducing spiffy new quilted-nylon jackets with double-front layers, the underlayer giving the effect of a vest. Some ''vests'' zip down the front and have turtlenecks. Others are in knits with appealing Nordic patterns that contrast with plain nylon outer shells.

It's only practical and inflation-fighting to keep a few tips in mind when you shop.

In buying sweaters, for instance, consider one size larger than your child needs right now. It can be worn immediately (sweaters are supposed to fit loose) , yet allow for a year of growth.

Check a child's closet before shopping. Often some items still are wearable.

It's best to take the child with you when you shop. But if this isn't convenient, carry a list of current measurements and perhaps a tape measure, so you can check garment widths and lengths on the spot.

Select jeans and slacks in slightly longer lengths that can be turned up for first wearings, then let down to accommodate fast-growing legs.

This also works for cuffs, especially on more expensive outer jackets. Manufacturers design them with ''grow cuffs,'' which are first worn rolled back several inches, then eased down as arms lengthen.

Elastic backs at the waist on pants, skirts, and dresses are a good growth device. They expand as more room is needed.

Units of several matching pieces, perhaps skirt, vest, slacks, shirt, and jumper, offer great mixing and matching possibilities and also coordinate with other items in a child's wardrobe.