The mood was indigo -- and indignation.

Homebuilders gathering at this center of extravagant taste and conspicuous waste seemed more like Spartans transplanted to Nero's Rome than typical convention revellers.

Many expressed depression and frustration, several anger, only a few undaunted optimism -- and these were generally the lucky ones within their decimated industry.

"They've been coming up to me at this convention and saying, 'If I could just sell the land that I have, I'll get out. I can't stand this anymore,' " said Frederick Napolitano, the new president of the National Association of Home Builders, at a press conference at the end of the convention.

Napolitano, from Virginia Beach, Va., is taking over leadership of an association that has been losing members as more and builders go bankrupt. Last year, 41 percent more of them went bankrupt than in 1980, itself not a banner year. This week's convention had 30,000 to 40,000 in attendance, about half of the number here four years ago.

"A sense of urgency hangs over this industry," Napolitano told reporters. "It was in the air as you walked through the halls of this giant convention center, as you sat in the committee meetings and as you listened to the debates on the board floor."

It is also an industry that has changed its mind about what the federal government should do for it. In resolutions approved here this week, the builders proposed that the Reagan administration subsidize interest rates on home loans -- down to 11 1/2 or 12 percent -- assure builders access to credit markets, and start a tax-favored savings program targeted specifically to housing.

A year ago this same group supported Reagan's economic policies, but as sales and profits evaporated during 1981, so did patience. This was clear from questions directed at administration officials who came here to offer condolences but little help.

"I want to be fair as far as housing is concerned, but we are not going to give a lot of deep subsidy out to housing at this time," Housing and Urban Development Secretary Samuel R. Pierce told the builders.

Pierce elaborated on what he has done for housing over the past year -- most of it a matter of not endorsing the total dismantling of long-standing housing programs.

He listed other accomplishments: retaining the Government National Mortgage Association, still under attack by the Office of Management and Budget; not sanctioning an elimination of mortgage interest tax deductions, a political sacred cow; continuation of a program for housing for the elderly and handicapped; consideration of allowing Community Development Block Grants to be used for construction, and helping make tax-exempt housing bonds workable.

Pierce seemed particularly proud of this last achievement. Communities have long been able to use tax-exempt bonds for housing, but the HUD secretary claimed credit for initiating technical improvements in Treasury regulations on the device. Getting his staff to talk with Treasury Department officials about the regulation was "a highly unusual -- if not unprecedented -- step," he told the builders.

An unimpressed Napolitano said he did not expect much assistance for the housing industry from Pierce: "He believes in the President's economic recovery program. . . . I don't believe he will fight to put in many of our programs."

Others builders expressed fear that only large corporations can survive in today's climate and will ultimately control the industry.

"We treat housing as an investment, but it is shelter . . . ," Martin Poretsky, a Washington-area builder, told Pierce, indicating that it would be unfortunate if the Merrill Lynches of the world were the only ones with enough resources to build housing in the future. "We represent an industry of productivity, and we need parity to build homes."

Financing was a major subject of this convention, with many believing that the public is unnecessarily fearful of the newer techniques intended to help people buy homes.

Robert Mitchell, president of the Suburban Maryland Home Builders Association, said his group plans to start a major education campaign soon, with the theme being that people are foolish to delay buying homes if financing is their main problem. Low-interest, fixed-rate loans are a thing of the past, Mitchell said, and people should take advantage of the plans that are available to ameliorate today's high interest rates.

In the meantime, federal officials are somewhat at a loss as to how to help the industry in the short term without adding to the federal deficit that they say is so largely responsible for the high interest rates.

"The problem is you are caught in the backwash of a general problem," Federal Reserve Chairman Paul Volcker told the disillusioned homebuilders. "You are at the end of the whip in terms of financial instability."