Diana and Charles left Washington yesterday morning under foggy, misty skies worthy of a Humphrey Bogart movie. The limited visibility grounded the Marine helicopter that would have ferried them to Andrews Air Force Base to catch their plane to Palm Beach. So they took the Rolls.

Their Royal Air Force jet had already been packed with suitcases and silver lockers, one a trunk clearly labeled "HRH THE PRINCESS OF WALES."

At the red carpet, Diana and Charles said their goodbyes to Selwa Roosevelt, chief of protocol, while last-minute luggage was hustled on, and Diana's lady-in-waiting, Anne Beckwith-Smith, and other members of the royal party scurried on board.

Before entering the plane, Charles and Diana (in a hot pink double-breasted jacket with black skirt, black stockings and shoes) flashed goodbye waves. About 250, undaunted by the wet weather, were there to see it. Some were on a return trip.

Thirty-year-old Cheryl Baxter, who lives on the base and had been in the front line of the throngs for the royal arrival, came back to see the departure. Her 9-month-old boy, Nathan, slept through the whole thing in her arms. "I couldn't do any better," she said as the couple's plane taxied away from the crowds. "I shook their hands, I got them to talk to me, I took their pictures. I said to the prince, 'My husband has ears just like yours.' He just looked at me and said, 'You say the nicest things. Thank you.' And I told the princess, 'I have three children, two of them the same ages as yours.' She said, 'Oh, that's lovely. Take care of them.' "

Baxter smiled. "I'm still kind of jello-y."

Within seconds of lifting off, the jet disappeared in the fog.

Gone but not forgotten.

The consensus: The crowds were good-sized and they were there to see Diana.

The lingering impression: She has a striking presence -- pretty, very slender, tall -- appearing taller than her husband and, some said, as tall as President Reagan. She has aquamarine eyes, a soft voice and an unpretentious, sometimes girlish manner.

She does indeed appear shy. She has made a habit of holding her chin down and looking up through her eyelashes. Though she appeared to speak comfortably with guests at events and made a few mischievous cracks of her own, she rarely said anything on the record to the press, she never made any public remarks, and her more private ones were impossible to overhear. Often, when her eyes caught those of the press, she dipped her head and turned it away.

But Charles didn't get short shrift. He was deemed charming, chatty and even versed on foreign affairs. He talked with Secretary of State George Shultz about Soviet leader Mikhail Gorbachev, with Mayor Marion Barry about urban city problems, with architects about city planning, and with Sen. Alan Simpson (R-Wyo.) about Wyoming.

Question: Who would decline one of the year's most coveted invitations -- dinner at the White House with Charles and Diana?

Answer: Robert Redford, that's who.

Whether the royal couple really met a cross-section of Washington is debatable. The British Embassy reception late Monday morning may have come closest -- mixing theater folk with arts patrons and Washington officials and media powers. But they never really got near many ordinary Washingtonians.

And at the three black-tie dinners -- the invitations to which were the most coveted -- there were only a handful of black guests. Opera singer Leontyne Price and her brother were guests at the White House dinner -- she was also the entertainer for the evening.

Barry and his wife Effi were the only black guests at the British Embassy dinner. At the National Gallery dinner Monday night, there were no black guests though there were some afterward at a reception for 500 at the gallery.

Elaine Crispen, Nancy Reagan's press secretary, said the White House list -- supposedly a national offering of people who would please the royal couple -- was made up "probably" by the White House social office with input from Buckingham Palace and the British Embassy.

"I just looked at [the list] and was told by people what a well-balanced guest list it was . . . what a cross-section of America it was," said Crispen. "Architects, the arts were represented, opera . . . Beverly Sills was seated next to the prince and they apparently had a wonderful conversation. He's apparently an opera buff . . . I see the guest list as a place where a lot of thought was taken."

At the British Embassy, the guest list was supposed to represent official Washington; the ambassador and his office were apparently responsible.

The lack of black guests "was entirely undeliberate, I must tell you," said British Embassy social secretary Elise Moore-Searson. "I don't think there was any specific reason. It worked out that way. They tried to find a cross-section of Washington. There was definitely no reason why there shouldn't have been more blacks. What can I say?"

At the National Gallery of Art, information officer Neill Heath said, "The guest list was put together by the gallery and the embassy for both the dinner and the reception. In both cases, we were really inviting trustees, executive officers, supporters and donors plus the embassy list. And that's just how it fell out . . . No attention was paid to who was black or white."

"He was so cute," beamed Judith Banks, the fiance' of Ambassador-at-Large Daniel Terra minutes after Prince Charles swept by them at the National Gallery of Art reception. "He asked when are we going to get married."

"I asked him if he'd come to the wedding," said Terra. "He said, 'Absolutely!' I said, 'You mean you'd go through another four days of this?' He said, 'It hasn't been that bad.' "

Left behind:

*A gift of two dozen Nathan's New York hot dogs at the Embassy Row Hotel, where some of the royal entourage stayed.

*A pencil drawing of Diana from Kimberly Facemyer of Ohio, who inscribed it, "To Princess Diana from your best admirer." It was propped up on a cabinet in a back staircase of the British Embassy, and unfortunately it never reached Diana, according to embassy officials.

*Damage, estimated at $700, to Philip Cook's Honda, parked in front of his house on Upton Street, across from the Washington Home and Hospice. Passers-by climbed over it to glimpse Diana when she visited the hospice Saturday.

Not left behind:

*After spending the night at the J.C. Penney barricade at Springfield Mall, 27-year-old Cheryl Adem of Fairfax stood in line waiting for Diana to shake her hand. Clutching a bouquet of pink and red carnations for the princess, Adem was ready to thrust them out when, six feet short of the woman, Diana ended her walk-about and went back to her car. Adem burst into hysterical tears. Diana, apparently moved, ordered the car to stop and dispatched a security man to retrieve the bouquet.

Still around somewhere:

*A man with a huge and remarkably good portrait of Diana, constructed from 10,000 multicolored jellybeans. He followed the flesh-and-blood princess all weekend, carrying his jellybean likeness.

Prince Charles had some impressions too -- of the "Treasure Houses of Britain" exhibition, for example. The exhibit, he told the crowd gathered at the National Gallery, reflected "the immense significance of patronage . . . individual tastes and indulgences of eccentricities on a grand scale.

"No committees here . . ."