Farrell Brickhouse has a photo album on Facebook comprising images of his friends' palettes. Lurking within each palette is the roadmap to the painter's process. Many thanks to Farrell for letting me post the images on Two Coats of Paint. If you aren't familiar with the artists' paintings, click on their names for links to their work, all of which is worth a visit.
(OK, this image is mine--snapped at the Bacon retrospective at the Met)