Hmm... with what I have right now (I haven't removed the link or css) all Google will see is a correctly markedup site. Yes I am using a CSS technique to colour some text / link but I cannot see that Googlebot would look at my links, look at the css, compare the background colour of #nav with the colour of the link, then make a decision about visibility (I could be using a pale yellow) and then make another decision about whether or not to use the link or demote me.
If every site were correctly marked up - maybe I'd give the bot some credit toward the idea, but as it is ? No, I cannot see that what I have is going to upset Googlebot / Google at all.
What I do agree with is Ozh's suggestion about getting others to do the same. I may well set up a link cat purely for Wikipedia links and include both my favourite links, new stuff and the spamcrap too.
Either way, I think Ozh's principle is sound - not only do we stop their spam, we counter their efforts too.