Complex sentence: During the painting phase, the painters see the lines as "descriptive bones" and color is used loosely, meaning the color is intentionally slightly "off register", highlighting the distinction between color and line.
Split into simpler sentences: During the painting phase, the lines are seen as "descriptive bones" by the painters and the color is used loosely. This intentionally means that the color is slightly "off register", highlighting the distinction between color and line.