A new version of the white theme for web interface has been published.
the article ID is ctx119509.
While I was updating this article I found a few things I thought I would share.
Someone in a different forum was trying to find the style sheet by searching for *.css. This sounds reasonable, in fact I did the same thing. The style sheets are aggregated together by an aspx page named styles.aspx.
The files themselves are actually includes and have the extension inc.
The best way to find them is to search for the word style.
There is a navStyle, fullStyle, etc.

Remember each of these style sheets is aggregated together. The Style closest to the element in question will supersede any previously specified styles.
I hope this info helps you customize web interface to look the way you want.