Because of the way text works in Processing, formatting individual words is hard in the general case.
Here is an example of formatting words in a text box: SentenceColoredText. It uses a “bricklaying method” to fill the space with text units.
https://forum.processing.org/two/discussion/comment/87679/#Comment_87679
Also, a small markup language for text formatting from @Chrisir :
https://forum.processing.org/two/discussion/comment/120813/#Comment_120813