Anyone printing in four color (CMYK) needs to know what RGB color space is best to work in. Sometimes software defaults are wrong. Two spaces in particular - sRGB and Adobe RGB(1998) - give very different results.

Here's the bottom line for two popular RGB color spaces:

sRGB - This is designed to simulate the average PC monitor. Good for images that will be shown on a computer or displayed on some particular device. Not good for print. Do not use for print. Adobe InDesign, depending on the version, defaults to sRGB. When this is the case, unexpected results will follow.

Adobe RGB (1998) - This is the preferred RGB space to be used for printing. Be sure that Photoshop AND InDesign are using this space.
It should be noted that all RGB colors should be converted to CMYK prior to printing. Use the wrong RGB space however, can have a big impact on this conversion process. Use of Adobe RGB (1998) helps to ensure the widest RGB gamut possible before conversion.

For a very brief read on the color spaces and printing, Color Space Fundamentals [3] might be what you are looking for.

For the ambitious, there are some excellent Color Mangement discussions. One in particular, Color Management: Photoshop Color Settings [4], gives step-by-step review.