The word "discolored" is correct and can be used in written English.
You can use the word when referring to something that has lost its original color, is not its usual shade, or is stained or blotched. For example, "The walls of the kitchen were discolored from years of smoke exposure."
The city advises on its site that "discolored water is safe to drink, but residents who are experiencing discolored water coming from the faucet should let the sediment settle before drinking".
The scientists noticed that the flash of the bomb had discolored concrete to a light reddish tint, had scaled off the surface of granite, and had scorched certain other types of building material, and that consequently the bomb had, in some places, left prints of the shadows that had been cast by its light.
At that point, according to Sullivan, all he had was "a pair of nostrils surrounded by a rim of shrivelled, shrunken, discolored cartilage".
Regent trickled the oozing inch-long gash with antiseptic and bound it with gauze and adhesive tape, whose excessive swaddling didn't make up for its being several years old; the tape was discolored, and barely stuck.
Here and there are skyscrapers built in the boom years of the sixties and seventies, their concrete carcasses discolored and crumbling.
A grubby white jersey with zippered neck, maker's emblem (Le Coq Sportif), big Union Jacks on each shoulder, and discolored glue bands across the thorax indicating the removal of perhaps a sponsor's name, perhaps the colored stripes awarded for some previous triumph.
The Times's Catherine Saint Louis reports on a rise in cavities and dental surgery among preschoolers: Devon's mother, Melody Koester, a homemaker from Stanwood, Wash., and her husband, Matthew, an information technology manager, said they began worrying about brushing Devon's teeth only after Mrs. Koester noticed they were discolored when he was 18 months old.
Zwick grounds the story in the labor and in the physical discomfort and irritability of townspeople living out of their element in ratty clothes, their skin withered and discolored from malnutrition.
For instance, in midtown at midday, most color seems to disappear, & you get a bone-colored clutter: a clutter bustling, bleached & dirty--dust-smeared glass, streaked aluminum, discolored brick, dirty concrete, potholed asphalt.
I saw that the beige carpet was worn away — not discolored or faded but just worked through by the ceaseless back-and-forth of my desk chair.
His skin, discolored and disfigured, resembled that of a leper, and it was impossible to guess his age.
