We examined molting, plumage abrasion, and seasonal color changes of Lawrence's Goldfinch, Carduelis lawrencei, to determine to what extent the reported brightening of male colors at the approach of the breeding season results from plumage renewal. Lawrence's Goldfinch has only one molt per year, a complete postbreeding prebasic molt. Color changes during spring result entirely from plumage abrasion and fading, not from a prealternate molt as previously was thought. The yellow breast feathers of the males, but not the females, are unusually resistant to wear, so that the yellow on the breast appears to expand and brighten, as less durable surrounding gray feathers abrade. This may be due to a one-third greater thickness of the rachillae of the yellow barbs in males, so that instead of the rachillae progressively losing yellow-pigmented material, the brown pigmented barbules break off, leaving intact the rest of the barb with only yellow pigment. In contrast, the yellow breast feathers of females abrade progressively at the tips of the rachillae. Females change dorsal coloration little, but males develop a yellowish area on the center of the back, which results when the olive to brown tips overlapping adjacent feathers wear off and uncover yellow proximal portions of neighboring feathers. We point out the need to examine plumage microscopically when studying molting and plumage changes so as not to reach false conclusions about the causes of the changes.