A gum resin produced by various East Asian trees, used as a yellow pigment and as a purgative in medicine. In Grahame’s Dream Days a sister criticizes her brother’s painting of trees because they’re blue. He retorts that they’d have been green if she hadn’t stolen his gamboge.
Source: Kenneth Grahame, Dream Days, illus. by Maxfield Parrish (Edin.: Paul Harris Publishing, 1983), p. 60