[dwig]

Originally Posted by AlexBell

Thanks, dwig, that's most helpful. Now to google CMYK.

I suppose you've found what you need, but for the sake of lurkers:

CMYK (Cyan Magenta Yellow blacK) is the 4-color colorspace used by most printing processes, particularly offset printing. It is also the colorspace used by the marking engine (that part that actually marks the paper) in common inkjet printer although their firmware and drivers are designed to swallow RGB (Red Green Blue) colorspace images.

RGB is the 3-color colorspace commonly used for digital capture and display. The output from digital cameras is generally converted from their raw sensor data into RGB images (TIFF or JPEG) either in-camera or using external conversion software (e.g. Lightroom, Aperture, Photoshop w/ Adobe Camera RAW plugin, ...). Computer monitors also work in the RGB colorspace.

For these reasons RGB is the commonly used colorspace for computer images while CMYK is the commonly used colorspace for artwork and images intended for output on printing presses.

The CMYK cover image is likely the result of the graphic image being originally created for use on the pbook's cover and not specifically created for the ebook. It is generally a simply matter to use an image editor that supports both RGB and CMYK to open the CMYK image, convert it to RGB, and then resave it. Conversion can result is some colors changing. A good program, like Photoshop, will offer the ability to select the color profile (ICM) and rendering method to help minimize the changes.

I've attached a copy converted to RGB