Most Americans, black or white or any other shade or combination of shades, realize we don't live in a color-blind society, and it's likely we never will. An Obama presidency would mean we have come to the point where we can deal with our failure to achieve color-blindness by being adult enough to recognize Obama's black skin does not mean he lacks the judgment, inspiration, political skill, (fill in your favorite trait), etc. to lead effectively. It illustrates a whole lotta non-black people accept a notion that would have been unthinkable 40 years ago, that they're willing to follow a leader with dark skin. They find Obama likeable and inspirational, in spite of his dark skin in some cases, and because of it in other cases.
This is very similar to JFK's issue with Catholicism and it's not insigificant that voters respond to Obama much the same way the responded to Kennedy. There was a lot of the same speculation at that time about Catholic block voting, backlash, etc. In the end, the nation went for inpirational, transformational leadership over a far more "experienced" vice-president. With a little help from Chicago, of course, but we're so pleased we elected Kennedy we don't like to be reminded Mayor Daley really elected him.
People are a lot more pragmatic about race these days than we used to be. We still have our prejudices, but we're not willing to dismiss a political candidate of another race because we've had so many neighbors, co-workers, etc. of other races and they proved to be just fine, better than some of the people we know who belong to our own race. We're trying to be cooler than we really are about Obama's race, pretending it doesn't matter. If we pretend effectively enough, maybe it won't matter.