The Doni Tondo by Michelangelo Buonarroti, Galleria degli Uffizi, Florence.
This painting made fools of some of 20th Century art historians. For a long time, they went on and on about how Michelangelo preferred to work in "browns and umbers" based on what they saw in the ceiling of the Sistine Chapel. So, when it was cleaned and all of these bright colors started appearing, the erroneous conclusion that Michelangelo preferred to work in dark colors had to be revised. Given that a work like the Doni Tondo was well known, they should not have been surprised.