By Andrew Chung and Nate Raymond WASHINGTON (Reuters) -Conservative U.S. Supreme Court justices signaled skepticism on Monday toward the legality of race-conscious admissions policies in cases involving Harvard University and the University of North Carolina that could imperil affirmative action programs often used to boost enrollment of Black and Hispanic students. The court heard tense arguments in appeals by a group founded by anti-affirmative action activist Edward Blum of lower court rulings upholding programs used at the two prestigious schools to foster student diversity. The justices h…