Color the Sequoia crew blue. The men of the Navy and Coast Guard who serve the presidential yacht are preparing to move on, a couple of the Coast Guardsmen bound for tugboat duty. Talk about comedowns . . .

To a man, crew members yesterday declared working on the 52-year-old vessel a dream assignment. An important one, too; a President needs to relax, they said.

The trouble is their new President views the Sequoia as a frill, expendable.

"The President would have enjoyed it," said Chief Yeoman Jim Cummings. "If he had had a chance to test it out, he'd have tliked it and probably kept it." Cummings looked sad.

So did Hull Technician Raymond Godman. He never ahd any doubt that he would help take President Carter down the Potomac after Carter's son, Jeff, showed up one Saturday to inspect the yacht. "After he got done looking at it," Gorman said, "he made the comment, 'It really looks nice.' Like his father, he's got a big smile."

Gorman's momentary smiled faded. "I came here last September," he said. "I was supposed to be here three years, with promises of probably longer. It wasn't so much the work we did on the yacht all winter. It was hearing my sister and my mother, hearing them say they were so proud of me. It's a bit of a letdown."

Such melancholy is understandable. Working on the Sequoia was a job that set the men apart. There were 31 Navy and Coast Guard personnel attached, with 14 aboard for each cruise. (The Coast Guard manned three speedy "escort" boats, which accompanied the Sequoia when the President was aboard and discouraged other boats from getting too close).

"I've been overwhelmingly proud to say I've been able to serve in presidential support status," is the way Storekeeper First Class Brian MacDonald put it. He said that getting a "clearance" to work on the Sequoia takes months, so thorough is the investigation.

The crew members trod where few were privileged to enter, a small, locked compound next to the tied-up yacht in the brown Anacostia. "You've got to have a reason," said a Navy public affairs man, who related that he had been to South Vietnam, the South Pole and around the world twice, had been stationed at the Yard for two years and had yet to be inside the Sequoia compound.

It was quiet inside the small building. One man was reading a magazine. Pool balls smacked in the next room. "It's a matter of cleaning up, packing up," said Brian Heselton, a Coast Guard electrician. "I feel useless now. We took a lot of pride in the yacht and our boats. And it shows."

It does. The chrome on the engines of the Sequoia positively glistens. "Those engines don't just look good, they work, believe me," said the man in charge, Lt. Cdr. Dewey Beliech, who showed a visitor around the 104-foot yacht.

He said most of the furniture had been hauled off to Camp David. The beds in the staterooms remained; the Sequoia could sleep six. It also could accommodate 40 guests for cocktails or a buffet dinner, 22 for a formal, sit-down dinner. Beliech pointed to what was the bar in the main dining salon. "During Franklin Roosevelt's time that was an elevator shaft to take him down to the staterooms in his wheelchair," Beliech said.

Making dignitaries (and such offspring as Susan Ford) happy made the crew happy: occasions such as Happy Rockefeller's birthday, Susan Ford's Fourth of July party, an Earl Butz working lunch. Earl Butz, who used the Sequoia as much as anyone, is a favorite among the crew, maybe the favorite.

"He always went out of his way to thank the crew for the long hours when he hosted a trip," said Master at Arms Chief Robert Matecki. "He didn't just stop at the commanding officer. Once, when we got back to shore, he had everybody on board applaud us."

Nor did Butz forget the usually forgotten men in the Coast Guard boats, according to one of them, Richard At Lee. (He said he spends much time explaining it's a British name and that's how he spells it; once, to prove it to somebody, he got his birth certificate, only to find it misspelled.)

"We stand off to the side when we get back from a cruise and people don't think about us," he said. Who knows about his most miserable night, a particularly cold one, when he thought he might freeze in his open boat? He was on special assignment, chasing after the Wilson Line because Susan Ford was aboard.

The crew has its memories, including many hellos and good-byes from normally inaccessible famous people, happy times, said ones, Nixon's final days. "Very tense," according to Heselton of the Coast Guard. Beliech was aboard for Nixon's last two cruises; he said the family asked for "complete privacy," that Nixon "looked very tired."

The mood changed for the better when President Ford came aboard but now - who would have thought this with a Navy man in the White House?- the mood has darkened again. "The President has made his decision," said Lt. Keith Curtis. "It's up to us to carry it out."

Curtis is accepting events stoically. This summer he would have taken command.