This is an account of studies of the function and evolution of colorful plumage in the House Finch. It is also an engaging study on the evolution of sexual selection in birds and a lively portrait of the challenges and constraints of experimental design facing any field investigator workingwith animal behavior. Part I sets the stage for modern studies of the function of plumage coloration with a review of the nineteenth and beginning of the twentieth centuries. Part II focuses on the proximate control and present function of plumage coloration. Part III takes a more explicitlyevolutionary approach to the study of plumage coloration using biogeography and phylogeny to test hypotheses for why specific forms of plumage color display have evolved. It concludes with an account of comparative studies that have been conducted in the House Finch and other cardueline finches andthe insight these studies have provided on the evolution of carotenoid-based ornamental coloration.