I actually saw one of these over the weekend. The new $20 bill is multi-colored. Released on October 9, 2003, the new bills are still mostly trademark green, but now include blue and peach colored areas. As they continue to release the other bills, they will each have their own unique color scheme, allowing you to quickly recognize a bill by its coloring alone.
The U.S. Bureau of Engraving and Printing issued a press release concerning the bills last Thursday. They’ve also devoted a whole section of their website to highlighting the features of the new bills.