When the Washington Convention Center opened three years ago, one critic commented that the big bland building needed one thing to bring it to life: "People, people and more people."

Through an April rain and chilly temperatures, I visited the convention center last Thursday to see some of the people. The starkly different conferences to which the center played host that day included the opening meeting of Jesse Jackson's Rainbow Coalition, and a conference called "Megamarketplace I," convened by D.C. City Council member Charlene Drew Jarvis (D-Ward 4), Katherine M. Bulow, the Commerce Department's assistant secretary for administration, and Gillian Rudd, head of the local chapter of the National Association of Women Business Owners (NAWBO).

On one side of the ground-level corridor were some 600 well-dressed businesswomen, several of them tucking morning workout sneakers into raincoat pockets at the coat check counter. They had come to market their products and services to 300 city, state and federal government representatives, as well as to corporate buyers as part of "Megamarketplace I."

"Women manufacture everything that men make," said Pennsylvanian Mary Del Brady, the new national head of NAWBO, "with the possible exception of sperm banks."

On the other side of the corridor were bluejean-clad farmers, progressive labor unionists, black elected officials, Hispanic Americans and women activists, who had come as part of the Rainbow Coalition. "We are the new majority!" proclaimed Jackson more than once, with a finger raised for emphasis.

While the businesswomen in their neat suits and sensible hair styles exuded an air of affluence and uniformity, they, like the Rainbow Coalition, were ready to roll up their sleeves and work. Women make up the fastest growing segment of business, but since women-owned businesses receive less than 1 percent of federal government prime contracts, their task of catching up is formidable. They came to this conference to meet with city, state and federal government representatives in an effort to open the federal market -- the world's largest -- to women business owners.

"This conference is a crack in the dam," said Rudd, head of Levine & Rudd. "We plan to have 51 percent of the federal procurement dollars by the year 2000."

As the women talked with government and corporate executives in a huge exhibit room and conferred with each other up and down the halls, workshops offering advice for doing business were in progress in smaller rooms.

Bulow, the Commerce official, blamed the low percentage of women-held government contracts on federal procurement officers relying on the convenience of the old boy network as opposed to looking for these new female entrepreneurs. "But if women can get that first contract, then they can get repeat contracts," she said.

Meanwhile, political change, as opposed to government contracts, was on the minds of delegates to the Rainbow Coalition convention, many of whom represented nontraditional support for Jackson from different industries, races and social classes.

At the morning news conference, Jackson vowed to build a "permanent progressive political organization" of groups that are disenchanted with Republicans and Democrats alike. "State by state and congressional district by congressional district," Jackson said, the coalition would organize nationally around defeating the Gramm-Rudman-Hollings budget- balancing act, opposing the Reagan budget and saving the family farm.

"We've already decided we've had about as much of Reagan's prosperity as we can stand," said Iowan Merle Hansen, president of the North American Farmers Alliance.

Following the news conference, coalition leaders, including environmentalist Barry Commoner, California Assembly member Maxine Waters, and William Winpisinger, head of the International Association of Machinists & Aerospace Workers, met in various committees with other delegates to create a charter. According to Jackson, it will detail the procedures for organizing the Rainbow Coalition across the nation.

Strolling around the convention center, I saw other groups meeting, but decided not to attend their conferences. The activities of the Rainbow Coalition and the Megamarketplace group had so stimulated me that I did not want to take a chance that another conference might unexpectedly bring me down.

As I left the Convention Center, I remembered that critic's words, and thought, yes, the Convention Center is alive and it has plenty of "people, people, and more people."