There are still things that happen in this country that involve racial business as usual. One such event involved the much-heralded visit of Prince Charles and Diana, princess of Wales. To the chagrin of many Americans, only four black guests were invited to the three showpiece events.

During three days of frenzied activities and ceremonies, the royal couple nightly mixed with a few hundred well-to-do or well-known Americans at exclusive black-tie dinners. But aside from Mayor Marion Barry and his wife, Effi, the only other black guests to attend were Leontyne Price and her brother -- and she was there to provide the entertainment.

The evening itinerary for Charles and Diana began on Saturday at the White House with a dinner that the Prices attended. When asked about the absence of blacks from the president's guest list, Elaine Crispen, Nancy Reagan's press secretary, said she 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 . . . architects . . . the arts were represented, opera . . . . I see the guest list as a place where a lot of thought was taken."

On Sunday night, the British Embassy hosted a dinner at which the Barrys were the only blacks to be invited. "I feel proud about that," said the mayor, "and sad there were not more."

According to the British Embassy, the ambassador and his staff assembled the guest list to represent official Washington. The sparseness of black guests "was entirely undeliberate, I must tell you," British Embassy social secretary Elise Moore-Searson said when she was questioned about their absence. "I don't think there was any specific reason. It worked out that way. They tried to find a cross section of Washington."

On the final night of their visit, Charles and Diana were entertained at the National Gallery of Art, where the hosts were gallery director J. Carter Brown and his wife, Pamela. On this occasion, not a single black was among the approximately 100 people invited to dine on quail and apricot mousse in pomegranate shells. Mayor and Mrs. Barry and Bishop John Walker, Episcopal bishop of the archdiocese of Washington and head of the Washington Cathedral, made the B list of 500 people who were invited to the after-dinner reception.

The National Gallery, positioning itself totally above the fray, insisted that its selections were totally colorblind. The gallery's 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."

Reflecting later on the absence of blacks at the showpiece dinners during the royal visit, Mayor Barry said, "We [blacks] are invisible again."

You can say that again, Mr. Mayor. If bad manners could be equated to sin, there are two kinds of sin operating here: one of omission and one of commission.

The point here is that it would have exemplified both sensitivity and good manners to have had gatherings that were truly representative of Washington and America for the royal couple. It would not be hard to quickly generate a list of blacks who, through their accomplishments, would have been good representatives had they been invited. But creating such a list is not the issue. Not having it is.

These events were yet another indication of what happens when you "leave things alone" and fail to put into practice some device to at least ask the question, "Is this gathering truly representative of a cross section of America -- its ethnic groups as well as its professions?" Moreover, it isn't as if the royal couple was not interested in reality, for in recent years, England has not escaped some of the problems of racial strife that Americans know well.

One does not have to be completely insensitive to blacks to achieve the results that were achieved during the royal visit. But it is clear that their absence did not seem to strike the persons who created the guest lists as a problem. Everyone insists that the selection of guests was totally colorblind. But I wonder if the list makers would have been equally colorblind if they had been hosting a party for the president of the African nation of Tanzania. Why does colorblindness always seem to result in the absence of blacks?