PERHAPS the most refreshing outcome of Colin Powell's flirtation with a run for the White House is that it has not prompted editorial writers across the nation to raise this question in their publications: ''Is the United States ready for an African-American president?'' Maybe there are whites who would vote against Powell because of his color. But this has not been showing up in any significant degree in polls. The only bias that remains is one that would be expected and is not threatening to racial progress: Some African-Americans would depart their usual Democratic vote and support Powell should he become the Republican or third-party presidential candidate. What makes General Powell particularly attractive to all races is that he is a black in public life who doesn't appear to have a black-related political agenda. He calls himself ''a fiscal conservative with a social conscience'' (like Eisenhower described his views) and in no way sounds as though he intends to stand out primarily as the candidate of blacks and other minorities. He does support affirmative action and says he is sensitive to the problems of the poor. But he makes it clear that if he becomes president he intends to be the president of all the people. Now Powell hasn't even stepped into contention for the presidency. Indeed, in his newly published memoirs he indicates an inclination against running. But as he nears his decision there is a widespread expectancy in the press and in political circles that this Gulf war hero and former head of the Joint Chiefs of Staff will make a big splash - whether he runs as a third-party candidate or enters the primaries (probably as a Republican). In his book, ''My American Journey,'' Powell says he's leaning toward a third-party candidacy. But a source close to Powell tells me that the retired general will indicate in November that he's getting into the GOP primaries. And if he does and is able to become the Republican candidate, he'll probably cut so deeply into Clinton's support among blacks that he will make it to the presidency. OH, I know what most polls of late have been showing: that Powell as a third-party candidate would pick up only about 30 percent of the vote and as a Republican candidate would not be able to push Bob Dole, Phil Gramm, Pete Wilson, and others aside. Perhaps. But I also remember polls of not too many months ago that showed Powell to be far and away the most popular possible contender to Clinton. Indeed, one poll showed Powell's popularity rating among Republicans to be up in the high 60 percent range - far above all other possible GOP candidates. Also, one new poll shows Powell's book tour is giving his popularity quite a boost. Yes, there are many indications that as an active candidate Powell might well capture the hearts of a high, and perhaps winning, proportion of the electorate. General Powell has a way about him that is so attractive. We saw it again and again as he stepped in front of the TV cameras to brief us on the Gulf war. It's so clear that he's in charge. Yet he has the quality that the voters treasure in their leaders: what is often called a ''becoming modesty.'' I mentioned Eisenhower before. Yes, Powell has so much of the charm that made just about everyone say they liked Ike. Ike had that big smile, too. Powell has a beguiling twinkle. If Powell doesn't win the nomination, he would probably do well enough to be the certain choice for the No. 2 spot on the GOP ticket.