On second look, it appears that I was wrong - "Use System Colors" looks like it only applies to the page colors, not the link colors. (The design of that window could be better...)
OK, here is what happens. By default, the browser will only use the colors you chose for links if the web page you are on does not set the colors. In other words, to see the colors you expect, you have to find a page that does not set their own colors (most do).
Below "Use System Colors" you can check "Use
my chosen colors..." but you won't like the results. It will use your green link, but it will destroy any page background images and background colors. You can view
this page in both modes to see what I mean.
