There are several ways to do Smalltalk code syntax highlighting on a web page. Pier has Pier-Shout, found on Lukas Renggli's Monticello repository. For browser-side highlighting, there are Alex Gorbatchev's Syntax Highlighter and Software Maniacs' highlight.js.
This site is using highlight.js. It is loaded in my Smalltalk rendering code thusly: