"The Red Piano" is generating plenty of green. Sir Elton John's three-year stand at the Colosseum at Caesars Palace in Las Vegas is notching sellouts, with 15 dates added to the 2004 run. John's deal at the Colosseum originally called for 75 shows over three years. Sources say his guarantee for the run exceeds $50 million. Since it began February 13, the engagement has grossed $14.5 million from 19 sellouts that drew 75,276 people. At John's current pace of $763,157 per night, the year's gross will exceed $30 million. Mark Juliano, president of Caesars, while not confirming John's guarantee, says the pluses to booking him go well beyond turning a profit at the box office. "It's about the traffic," Juliano says. "It's about image-building for the property and ancillary transactions people make at the restaurants, retail, bars, and, most important, the casinos." Juliano adds that Caesars has seen a "nice little uptick" in that regard surrounding John's shows. "The Red Piano" resumes July 23 and ends August 8; the additional 15 dates run between October 12 and 31.