Not only has Apple given its iMacs a colorful upgrade, but it has also restored its monochromatic logo to its former rainbow glory. As Design Boom notes, however, the revival of Apple’s colorful 1977 logo doesn't exactly match the original.
40 years after Rob Janoff designed the original bitten Apple logo, the company is returning to the rainbow blueprint, albeit with some subtle modifications. As you might notice, each of the color bands is rendered in a slightly darker, duller hue. Don't expect this multi-colored version to be taking over any time soon. Design Boom suggests that this particular iteration of the iconic logo is probably “a one-off for the iMac launch rather than a complete remake of their rainbow logo.”
Janoff originally included the colored stripes to indicate that Apple machines had color screens. Each stripe was printed in its own specially mixed color—at a considerable extra expense which Jobs approved because he felt the more vivid colors improved people's emotional response.