"We must be cautious," said one speaker. "Sensible," offered another. $1A third member of the same group warned: "We cannot be too optimistic" or "overcome by euphoria." All agreed: "We refuse to rubber-stamp this program."

No, these aren't sour notes from a seminar of conservative CPAs; there was not a single green eyeshade or wing chair to be found in Room 6202 of the Dirksen Senate Office Building when these sentiments were expressed. Nor are they quotes from traditional economists. They are from moderate to liberal Democratic senators on the Budget Committee on the occasion of its opening session Monday. Some change, you might observe.

Change. That's what this week's Senate Budget Committee hearings have been all about. First, the committee had assumed the task of deciding where to reduce federal spending by more than $150 billion over three fiscal years. That's not small change.

The Budget Committee today has its first-ever Republican chairman, Sen. Pete V. (nee Pietro Vichi) Domenici of Albuquerque. Vichi was the surname of the chairman's Italian immigrant mother when she met his Italian immigrant mother when she met his Italian immigrant father. Not too long ago, there wasn't a Pete or a Domenici on any roster of leading Senate Republicans. Henry Cabot and John Foster were more the style. That's no small change, either.

Domenici, like all his party colleagues who are now committee chairmen, is without a Republican role model. Only two of the current GOP chairmen were even in the Senate during Ike's first term in the White House, when the Republicans last ran the place. But that's still not much help, because one of the holdovers, South Carolina's Strom Thurmond, was, during that period, a Democrat. But then he changed.

Not too many semesters ago, some of us Democrats figured we knew a thing or two about change. It was, as everyone knew, inevitable. But change, as only a few grasped, was really progress traveling under an assumed name. That is not a majority point of view today.

Now, most change seems to be individual. People who study such things tell us that there are three very major changes to be dealt with in the life of the contemporary American grownup: change in occupation, change in a close personal relationship and the change involved in moving from familiar to unfamiliar surroundings. Any one of the three can be quite difficult.

This week, Room 6202 of the Dirksen building has been nothing short of a laboratory demonstration in radical change. For the Democrats, a lot more than their rhetoric has changed. In occupation, they have been reduced to the minority. Several of their close colleagues have departed since last November, and the unfamiliar surroundings, away from the gavel and the microphones to the power, require some real getting used to.

Some changes, of course, are less wrenching than others. Generally the adjustment to power is much less difficult than the adjustment accompanying separation from power. Most Republicans seem to be getting the hang of it. In fact, freshman Indiana Sen. Dan Quayle, perhaps realizing that the cameras would be pointed toward the Republican side of the committee table, showed up wearing television blue -- suit, shirt and tie -- and a truly remarkable March tan. Quayle and his tan made the evening network news.

But the Democrats are facing even more serious changes. Of 10 Democrats (there are 12 Republicans) on the Senate Budget Committee, five of them -- Chiles of Florida, Metzenbaum of Ohio, Moynihan of New York, Riegle of Michigan and Sasser of Tennessee -- face reelection in 1982. In 1976, when all five last ran, Jimmy Carter carried all their states except Jerry Ford's Michigan. Last November, Ronald Reagan won all five states. In fact, Ronald Reagan won the home states of all 10 Budget Committee Democrats. Numbers like those, by themselves, do not abbreviate a presidential honeymoon. And such numbers are for now given more attention than Gallup's scientifically selected 1,363 adults.

But while criticism of the president among congressional Democrats remains mostly muted, that is not the case in regard to David Stockman. Reagan's 34-year-old budget director didn't carry anybody's state last November, and his public manner in recent committee appearances does not remind anyone of a total-immersion Dale Carnegie course. By now, Stockman must be tired. And he is testy. Diffidence and David Stockman are not in the same car pool.

Whether by strategy or stumble, Reagan and Stockman are fast becoming for some Democrats the good cop/bad cop pair from detective stories. Stockman plays a less colorful if more pedantic Kojak to Reagan's better-tailored Columbo. At the current rate, Stockman's critics should be reminding us soon that he lacks the basic Republican credential for government service at any level: He has never met a payroll.

Still adjusting to the changes in their lives, the Budget Committee Democrats continue to argue among themselves over where to cut. The Republicans on the committee, still acting more like the disciplined minority they so recently were, have been generally united. The Democrats have been fighting among themselves just like in the old days, when they had the votes to make a decision and make a difference. Just one more change.