For 2006, two additional colors were added to the line up, Spice Red Metallic and Brazen Orange Metallic, while Midnight Blue Metallic and Yellow Jacket were dropped. Changes for 2006 included revised blacked-out tail lamps, illuminated steering wheel radio controls, faster moving power seat motors, and an interior power door lock switch. The climate control button for the A/C also had the word "Defog" added to it for the 2006 model year. Along with the 2005 model, the 2006 GTO was equipped with the 400 hp (300 kW), 6.0 L engine.
On February 21, 2006, Buick-Pontiac-GMC General Manager John Larson announced to dealers that GM would halt imports of the GTO in September, making 2006 the last model year for the new GTO. He stated the main reason for the cease in production was the GTO's inability to meet new airbag deployment standards that were going into effect in 2007. This fate should have come as no surprise since this generation GTO was only intended as a limited production run for those 3 years from the beginning of the program.
Source: Wikipedia, 2011.