off-color
off-color or off-colored {adj.}
1. Not of the proper hue or shade; not matching a standard color sample.
The librarian complained that the painter had used an off-color green on the walls.
2. {informal}
Not of the proper kind for polite society; in bad taste; dirty.
When Joe finished his off-color story, no one was pleased.
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Source: A Dictionary of American Idioms