The blue-suited buoyancy around the room, or the plain old-fashioned grins as direct-mail czar Richard Viguerie described it, was proof that "it was a great time to be a conservative. There's nothing but grins in this room."

The smiles over rich chocolate truffles and chicken and snow peas kabobs at businessman Peter Hannaford's office were related principally to the passage of President Reagan's tax cut proposals by the House. "Mr. Reagan never ceases to amaze me with his ability to persuade," said Viguerie. The mood at the White House was described by press aide Karna Small as "jubilant," and the long day in the Oval Office was capped by Champagne and the president leading a round of birthday songs to special assistant Elizabeth Dole.

The crisp linen suits and white summer dresses belonged to a small conclave that one guest described as "the right and the righter," and the guests went from A (National Security Adviser Richard Allen) to B (columnist Patrick Buchanan). In between counting new Democratic converts to the president's economic solutions, there was posing for pictures with Tsai Wei-ping, the representative of the Coordination Counsil for North American Affairs, the official Taiwan representative in the United States. aBut there were also snatches of "Awacs" and "Neumann," references to the case of the U.S. Ambassador to Saudi Arabia who suddendly resigned on Tuesday.

Hannaford, whose clients range from General Motors to a group of Guatemalan businessmen, was telling Allen in explicit detail about his fishing trip Monday off Atlantic City, which garnered a bountiful case of blues. Another fishing trip, with Hannaford talking to a group of investors about buying The Washington Star, wasn't as successful. "Some friends called me and asked me to call about four people. They all agreed with the principle of saving the paper and having two-paper competition, but they weren't that interested in plunging in."

Allen hadn't talked to his good friend Robert Neumann about his abrupt departure from the diplomatic corps, which was reportedly caused by a rift with Secretary of State Alexander M. Haig Jr. "I am saddened by his resignation. He is a scholar and a diplomat. I don't know what caused it," said Allen.

Wei-ping, a career diplomat, said he feels U.S-Taiwan relations, which were reduced when the United States established full diplomatic relations with Peking in 1978, are now improving. "I feel as if I am surrounded by friends," he said. "When I deal with AID and other government organizations, there's a much friendlier atmosphere." Richard Stone, the former Florida senator and now a lawyer in Washington, has worked with Taiwan on the shoe import quota issues. They were lifted by the administration last month, but Stone declined to discuss any new era of bilateral relations.

Barbara Thomas, the youngest, and only woman, commissioner of the Securities and Exchange Commission, was encouraged by the House action on the tax cuts. "The job of the SEC in the 1980s will be to facilitate capital formation. The reduction of capital gains tax will encourage people to invest."

After the president's victory, he had a series of congratulatory congressional telephone calls. "The president was kind of cute," said Karna Small, who had received a series of the president's doodles, penned during the Ottawa summit conference last week. "When he was on the phone with a bipartisan group, he said, 'The Democrats were very gracious, now don't you gloat.' He said it was a great day for America. Then he said to Jack Kemp, 'You want a 30-percent tax cut during my second term?'"