Variations on the built-in admin color schemes. Shows visited links in a different color for easy tracking of dashboard news items not yet read.
I used the same color the built-in color schemes use for when you hover over a link.
Nope, and it never will. You really should upgrade WordPress anyway to keep your site secure.
It might work. I listed the plugin as requiring at least WordPress 3.0 because I have not tested older versions.