If they had verbal agreement it is not graffiti.

The dictionaries disagrees[1][2], but lets call it graffiti-styled street art then. Guess graffiti is perhaps a bit more a general term here[3].

[1]: https://www.ahdictionary.com/word/search.html?q=graffiti

[2]: https://www.britannica.com/art/graffiti-art

[3]: https://snl.no/graffiti