MEXICO CITY — “How dark! No! How ugly!” a Mexican social media star exclaimed after accidentally using a filter that darkened her face during a live broadcast on Instagram, reigniting the country’s longstanding debate about racism.The remarks by Barbara de Regil, a popular actress in movies and soap operas, came as Mexicans are engaging in their own conversations about racism after the death in the United States of George Floyd, an African American, under the knee of a white police officer.In Mexico, the debate has centred on discrimination against indigenous groups, who have long suffered from poverty, isolation and a lack of representation in politics and popular culture.With many Mexicans still confined to their homes by the coronavirus