If you visit Ask.com at http://www.ask.com/ today, you will notice that the Ask.com home page is green. They have changed the color from red for St. Patrick's Day. In the past Jeeves dressed up; see March 17, 2004 and March 17, 2005. Clicking on the Ask.com green logo takes you to a St. Patrick's Day search as does with Google and Yahoo! (takes you to a non search page) that are also sporting logos for the special day. However, Ask.com's inner search pages are still red, and so is http://uk.ask.com/, however, they do have a special link to a St. Patrick's Day search.
Forum discussion at Search Engine Roundtable Forums.