Designing Disney: Imagineering and the Art of the Show by John Hench has seen two releases. The purple one (referred to as Hench Purple) was 2003 and the orange version was released four years after his death in 2008.
The purple cover is classic Hench and shows how much power he wielded at Disney. Even in 2003, it wasn't a modern cover and felt dated. After his passing, Disney re-designed the cover to make it more modern, especially with regards to color. There's not much difference between the two editions, text-wise.
When I am asked, "What is your greatest achievement?" I answer, "Disneyland is our greatest achievement. Disneyland was first and set the pattern for others to follow." Disneyland has been an example for many enterprises in the entertainment industry, and its design principles have been embraced by other industries as well. The concept of "themed" environments--places designed so that every element contributes to telling a story--was developed and popularized by Walt Disney. Its influence has been extraordinarily widespread, and can be seen today in many aspects of our daily experience--in shops and shopping malls, hotels, restaurants, museums, airports, offices, even people's homes. --John Hench, p. 1.