Here is a working version of what you wanted.
The important steps were:
i) put the SVG in a regular element (vs. HTML widget). This is equivalent to using SVGs inline on a regular web page;
ii) Use a jQuery selector to alter it (it would probably work with regular js too).
You (and anyone else) will need Hype 3.0.4 to open this file as that is what was used to create it
SvgTest_working.hype.zip (49.9 KB)