There is (or was) a pretty smart reverse graffiti in a tunnel of Brussels, Belgium.
The tunnel's walls are covered in white tiles, but are all black because of the cars' pollution. The graffiti goes in two parts (written in French), facing each other:
* "LE MAL PROPRE" - meaning "the shoddy" has been written by cleaning the tiles composing the letters, hence white letters over a black background.
* "LE BIEN SALE" - meaning "the pretty dirty" uses the opposite technique: the tiles outside the shape of the letters have been cleaned - black letters over white background.
* by the way how the words are revealed: cleaning the letters or their surrounding
* by the play on words in the two commonly used expressions: "mal" - badly - being the opposite of "bien" - well -, and "propre" - clean - being the opposite of "sale" - dirty:
* "mal" has a negative connotation and is used with "propre" which has a positive one.
* "bien" has a positive connotation and is used with "sale" which has a negative one.