Possible Clues:

• Crude torture on backstreet used, for example, by Munch in versions of The Scream
• Painter's media
• Source of crude pictures?
• Colors used by Rembrandt
• An artist may use them in a spoilt sort of way
• Some canvas covers?
• They're put on canvases
• Ring -- it's transformed with plain colours
• They are put on canvas in topsail at sea
• Seurat supplies