As Josephine K. Tarvers discusses in her article, "'The Deep Still Land of Colours': Color Imagery in 'The Defence of Guenevere and Other Poems'", Morris uses color imagery to symbolize meaning. The color red illustrates love and lovers, which is used in this line when Launcelot arrives to Guenevere's rescue. Morris, influenced by the traditional color scheme of the Middle Ages, uses colors such as red, green, white, and blue in his works to evoke an emotional response from his readers. https://www.jstor.org/stable/4174266