There seems to be some logic to show some search engines in a different color, but I can't figure it out. Is it just until something (any single character) is

There seems to be some logic to show some search engines in a different color, but I can't figure it out. Is it just until something (any single character) is typed into the search input box? edit: the purple color was just the "visited" link color. The link color changes because the links are updated to include the query (thus changing the visited status.)