code-prettify works by adding
<span class="..."> elements into the prettified code with classes for different syntax elements. The supported elements for
lang-vb are "plain", "string", "comment", "keyword", "literal" and "punctuation".
The colors themselves are controlled by a stylesheet provisioned by Stack Exchange (you're looking for
primary.css), so SE gets to tweak the colors anytime they want, and nothing needs to be pushed to Google's repository for that to happen.
lang-vb is used for all "flavors" of VB, including vba, vb6, vbscript, but also vb.net.
Looks like there was a CSS update from SE — explaining why there isn't any pull requests on the repo you linked — to make VB syntax highlighting look more like VB.NET does (by default anyway) in a modern IDE like Visual Studio:
The default syntax highlighting in the VBE wasn't all that great anyway (
lang-vb used to look similar to this, at least as far as keyword-blue is concerned):
Personally I like configuring the VBE's identifier text forecolor to teal - it makes string literals (whose forecolor isn't configurable) neatly distinguishable from identifiers:
I wish the VBE allowed different colors for type names vs other kinds of identifier names, but 1998 doesn't agree!