With the tip of her palette knife, Katie Runde picked up dabs of paint from her palette and dropped each into the center. She blended them, moving the knife in quick, tight circles. She turned the paint over, mixed it some more and held a dollop in front of her model’s face to gauge the match. “Nope.” She added colors, mixed, scraped and scrutinized again. Still no. “Oh, God,” she whispered. “Why is it so hard?” First there was the matter of a smile. Runde couldn’t produce a portrait of Alexander Twilight wearing the scowl she saw in the photo she used as a guide — the only image of him known to exist. True, the 19th-century Brownington minister and school headmaster had been strong-willed and strict. He built a four-story granite dormitory after school trustees said no. He expected students to study 10 hours a day and disciplined boys with a leather strap, but he was also known to amuse them with his sly, satirical humor. One would later recall his “mirth-provoking face, the jest-loving propensity, the perennial fun.” Runde wanted her portrait of Twilight, which was headed for the Vermont Statehouse, to convey that warmth. She had to figure out how a smile would change the rest of his face, his eyes, his forehead. Now she mixed his skin colors. Accuracy was paramount but elusive. The tiny daguerreotype was black and white, and former students had described Twilight only as “bronzed” and “swarthy.” Twilight today is celebrated as the first person of African descent to graduate from an American college, Middlebury, in 1823, and the first Black American to be elected to a state legislature. But the accomplishments are complicated by the fact that most Vermonters at the time perceived Twilight to be white. Runde’s skin-tone model was Demetrius Borge, a 2016 Middlebury College grad, filmmaker and photographer who shot as the artist worked. For hours, he documented her process, pausing to stand in front of her as she parsed his face into titanium white, yellow ochre, cadmium red, burnt umber, cobalt blue, black. In the footage shot by Borge, Runde studied another hue. “It needs to be lighter, now that I’ve made it darker,” she said. She added color, circled, scraped and held it up again. “Now it’s too light.” “And to think,” she said, “that there are usually paint colors called ‘flesh tone.'”…