(IDEX Online) - Tiffany & Co fooled some of its Instagram followers when it revealed it was introducing a bright shade of yellow as its new house color, to replace the iconic robin-egg blue.The 1 April post, simply showing a yellow box (pictured) and the message "tiffanyandco Introducing our new House color. #TiffanyYellow #TiffanyAndCo", attracted over 420,000 likes. It was, of course, an April's Fool prank.Tiffany sets great store by its particular shade of blue - Pantone 1837 (named after the year the company was founded) - and had it trademarked in 1998.AdWeek, the brand marketing bible, once described the Tiffany blue box as "very possibly the most recognizable and most desired retail container in history."