Colorado Gov. Richard D. Lamm started his second four-year term this week hot off a protracted confrontation with leaders in the black community and a good distance from the image of a new liberal spokesman that he carried into office with him in 1975.

Lamm, 43, who began his tenure as chief executive with a reputation as the environmentalists' champion and a spokesman for social causes, entered his second term as a seasoned politician who has traded the politics of confrontation for the "realities" of running a conservative, growth-conscious, tight-fisted state.

The governor, who won a landslide victory in November over ultraconservative Republican state Sen. Ted Strickland, said of himself, "There's no question in my mind I've had a hard dose of political reality therapy" the past four years. But he denies that he has changed his political philosophy from its basic liberalism or that he has put on the cosmetics of conservatism for political advantage.

But if Lamm's essence has remained the same over the years, his aura has changed.

Last week, the governor faced an angry gathering of black elected officials and community leaders who demanded that he pay his lieutenant governor, George Brown, his December salary. Lamm has withheld the money because, he says, Brown, a black man, deliberately and willfully overspent his budget by $10,000.

Although Brown had been a source of controversy and embarrassment even to black leaders during his four years in office, he had become a symbol of black achievement in the state and an avenue through which blacks would vent frustrations over what they felt was Lamm's decreasing sensitivity to their needs.

State Rep. Arie Taylor, a black Denver Democrat and probably Lamm's most virulent critic in the legislature, said the governor "apparently has gone to bed with the Republican Party and has been willing to sacrifice the Democratic Party."

"I don't think Dick has changed radically. We never knew who he was until four years ago," she added.

If the perceptions of legislative and business leaders are accurate, Lamm has altered his behavior significantly as a result of political realities he knew little of when elected.

In the 1978 campaign, the governor "succeeded in reapproaching the business community. He worked hard to portray himself as a friend of business," said Colorado's newly elected Republican senator, William Armstrong.

Bruce Rockwell, chairman of the Colorado National Bank, agrees, contending that Lamm has a better understanding of the role of business in public policy today than in 1974, noting that the governor seems to have learned "hand-wringing isn't enough" to solve complex growth and economic problems.

But courting business isn't what Lamm was known for when he first took office.

"He's the kind of person who likes to ride a rising tide but not stick with it," said Carolyn Johnson, a local environmentalist. Apart from air pollution legislation, which Lamm has made his top priority in this legislative session, Johnson said, environmentalists should expect very little from the governor.

For his part, Lamm concedes that the environmentalists have some cause to view him with disappointment. Lamm, who gained a national name for himself as a strong environmentalist while running for his present office in 1974, admits to a "big falling out" with environmentalists over water policy. He has backed some Colorado water projects, and calls environmental advocates "hopelessly naive" in their blanket opposition to such projects.

Lamm asserts that he simply is facing the facts that new, bold programs stand little chance in light of the stacked deck of Republican majorities in both houses of the legislature that he must confront.

"It would be like the statute in the park," he said two days before starting his second term. "The pose is heroic, but it gets you nowhere. I don't want to be the statute in the park."