We can see oil discoloring the ocean, blackening coastlines and covering wildlife, but carbon dioxide is colorless and odorless.

CNN: What if carbon dioxide were as black as oil?

The all-pervasive sea water still left its mark, seeping into the frames and discoloring them with salt stains and algae.

CNN: March 11, 2013 -- Updated 1910 GMT (0310 HKT)

Over the next several months, the erstwhile housepainter whitewashed the brick, discoloring his lime with pigment to give the walls an ancient tint.

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