Graphic designers, architests, building administrators and federal workers concerned with design came to learn at the Federal Design Assembly at the historic Pension Building yesterday.

But when they walked into one lounge, they did a double take. At first glance, it looked like all those Government Issue Drabs they had to come to the Design Assembly to denounce and lear how to improve.

The room was full of hall-wall cubicles. Each had a framed color picture of Jimmy Carter, a telephone and a desk turned so you can't get your legs under it. Some of the desks and small defects - a bit of spilled paint here, a misadjusted leg there. (The desks are made by Art Metal. Inc., currently involved in a controversy with the General Services Administration over the quality of some of their sales to the government.) On the walls at each desk was a mirror with a man's shape on it, permitting the government worker to talk to himself.

The room is a sproof, a satire on the usual government design, a visual joke by architect Stanley Trigerman. "I may look straight," said Tigerman, a nationally known architect. "But I'm really off the wall."

He said he hadn't known about the Art Metal controversy when he chose the furniture to make his point. "I'd picked it because it was your typical GSA stuff."

The room and the next one, also by Tigerman, are painted with red and white stripes and stars on a blue ceiling.

The second is called a "Maize for the Administrator." Walls of blue-wrapped bond paper and yellow-lined pads are encircled with red tape and tied in a bow. Within the maze are office chairs and telephones - all on the same line so everyone can listen in on the other.

"If you make it through the maze, you don't get a prize, you just get out." said Tigerman.

Jay Solomon. GSA administrator, said he found the exhibits funny.

Tigerman was one of the four nationally known architects asked by Roy Knight of the National Endowment for the Arts architecture section to design lounges using furniture available from the GSA catalogue. "We asked them to use imagination and illustrate good design."

Solomon, speaking in a keynote address yesterday morning said. "I didn't come to Washington to continue "business as usual" in drab, gray, sterile shells that are so uninviting to the general public as well as the people who work there.

"I came to Washington because I shared President Carter's ideals and hopes for a bright new day, a day in which efficiency, openness and respect for one another and for the environment are the prevailing concepts . . . and those concepts should be reflected in the government's buildings.

Solomon, who is currently involved in a massive effort to clean up the scandal-plagued GSA, went on to promise. "No longer will the nation's business be transacted behind plaster walls and closed doors but in openness where whole floors of people work together in harmony . . . No longer will buildings be darkened at 5 p.m. and locked up tight when the last workers leave. Public plazas, courtyards, audtioriums and lunchrooms are being thrown open to the people of all sorts of community events ranging from shows to concerts."