THE HIGHLAND Indians (about 60 percent of the 7 million population of Guatemala) living in mountains as high as Switzerland, and valleys as deep as the sea, are still weaving their own textiles.

Blouses, ponchos, trousers, belts, skirts, headpieces and shawls from about 40 Guatemalan villages -- all part of the private collection of Mr. and Mrs. Henry A. DuFlon -- are on exhibit through October at the new Organization of American States building, 1889 F St. NW. The DuFlons, who live in Antiqua, Guatemala, have been collecting the attire of the Mayan Indians for 20 years.

The exhibit is well-arranged, with separate displays for each village and includes fine photographs of Highland Indians by Barbara DuFlon.

Each community (there are more than 100 of them) has developed its costume, every one strikingly different in color, style and design motifs from the others.

DuFlon writes: ". . . over the past 100 years (and continuing to the present day) the Maya of Guatemala have utilized a greater variety of weaving skills and demonstrated greater diversity in the arts of design and color, than any other ethnic group in the world."

The colors are vivid: cochineal reds, shellfish purples, indigo blues, spiked with occasional yellow accents; the fibers are usually cotton. Stripes are everywhere, often with designs woven or embroidered within them. One particularly appealing pair of trousers is made of tightly woven cotten in striped purple and cream, with a wide band of brightly embroidered birds and flowers from about the knee to the ankle.

Two types of looms are used. Women, weaving the exact amount needed for one garment in their own homes and for their own families, use the backstrap loom. Simple and portable, it dates from before the arrival of the Spanish in the 16th century. The footloom, traditionally operated by a man, produces wider cloth in lengths of many yards, often intended for commercial sale. The designs, especially those produced by the backstrap looms, are extremely imaginative and sophisticated. Many of the village weavers are now members of the nationwide Federation of Artisan Cooperatives, helping them to receive a fairer return for their labor and materials.

When you have whetted your appetite by seeing the OAS exhibition, you might want to visit some of the shops in Washington selling Guatemalan textiles.

Amanda Lasker, owner of GOSSYPIA, 325 Cameron St., Alexandria goes to Guatemala several times a year to select textiles. She comes back with a wide assortment of bolts of handwoven cotton materials in lush colors, mostly stripes ($8.50 a yard, 36 inches wide) and some solids ($6.50 a yard). She brings indigenous costumes: blouses and ponchos (unseamed sides), which cost $25 to $200 for fine examples, and pieces of backstrap weaving two or three yards long (around $100 each). The latter are used by the Mayan women to wrap their heads and shoulders, their babies, and whatever else they want to carry. These fabrics could be used in an American home to wrap anything and everything: cushions, beds, tables, windows or even the whole house a la Christo. The material is machine washable (but probably should not be machine dried) and needs little or no ironing.

A nearby shop, NUEVO MUNDO, 313 Cameron St., Alexandria, offers an especially good selection of authentic Mayan blouses and ponchos, from $100 to $150. The colors and patterns are spectacular, they can be washed in cool water, and look as though they would last a lifetime. Nuevo Mundo also has dresses made of Guatemalan cotton, designed for export, very stylish and very reasonable. For example, a good-looking two-piece black dress with a tiny trim of red print costs $44. It would seem ridiculous to pay twice as much for an uninteresting made-in-U.S.A. dress.

THE G STREET REMNANT SHOP, 805 G St.NW, carries Guatemalan handwoven, striped (sometimes with small designs within the stripes) cotton material by the yard ($7.95 a yard, 36 inches wide). Manager Hermine Dreyfuss will help with ideas and how-to-do-it information for making bedspreads, curtains, clothes, etc. Dreyfuss designs and makes her own clothes and often uses Guatemalan fabrics. She says they wash beautifully (may fade a little but never run) and are very good for traveling. They don't crush.

LINDA McGLATHERY sells authentic costumes and textiles by appointment only. Call evenings 234-4444. She will come to your house. Her pre-Christmas sale will be held at her residence on Nov. 14 and 15.

The two PAN AMERICAN GIFT SHOPS, 1889 F Street, NW, and OAS Building, 17th and Constitution Ave. NW, carry Guatemalan blouses, shawls, skirts, etc. Prices are reasonable.