He has touched about every base in the spring fashion game: bright colors, slim shapes, tapered suits, sailor suits, dots. And because he has done them so tidily and tastefully, Richard Assatly is being touted as one of the important new young designers of the season.

But he is neither new nor young Assatly, 34, has seven years' experience as a designer for Ginala, after graduating from the Fashion Institute of Technology and then working as an assistant to designer Pat Sandler. He has had his own firm with partner Gino DeGeorgio for three years.

"It's all those years as a coat and suit designer that makes him so good in this period of tailored clothing that is ahead," says Larry Conzales of Saks Fifth Avenue. And "his color sense is great", says Joan Karl of Garfinckel's. Both stores, among others, will carry the Assatly spring collection in Washington."They said I had no color sense at all at Ginala," laughs Assatly. "But in that period I just couldn't see women walking around in bright colorful coats."

Color is now the big stimulus, he says. "When you have taken away to many of the details, and clothes are so simple, you need color for excitement, like texture."

He turned on to color this season as well as white, slim lines, belted suits, straplessness and all the other current themes, he says, because "it's what is in the air. Talking to people, reading, discussing clothes with colleagues, going to Studio 54, shopping the European fabric market, all those things tune us into the same wavelength about clothing."

As he worked on the collection, starting three months ago, he shortened hemlines every week. "The more narrow the clothes became, the more the longer length looked drippy," Assatly says. As a result, most of his skirts are cut off just below the knee.

But in one respect, he differs from many other designers: His insistence on keeping prices where they were last year. Part of the reason is that clothes have fewer parts and layers. "A lot of pieces always add up to more than one dress. That's why evening clothes are always less expensive for us than daytime things," Assatly says.

With both labor and fabric costs up, uncomplicated clothes are big assets in holding prices down. "No one wants a suit today with the intricate darting and complicated seams we used to make," says Assatly. "Can you imagine, we once made suit jackets with eight-piece gussets in the underarm. It's admirable, but who cares about that now?"