Sara,
There are two different "rainbow series" that I am aware of as relates to computers:
One relates to CD encoding standards and appears to be the close to what you are talking about -
Orange book - specification covering writable CDs, including CD-Rs
Green book - specification covering CD-I (compact disc - interactive)
Red book - standard for audio CDs
White book - specification covering the video CD format
Yellow book - specification covering CD-ROMs
The other "rainbow series" that I am aware of is the US Department of Defense book series on Computer Security. There are more than 20 books in this series, each with a different color. Take a look at the following website for a listing: http://www.radium.ncsc.mil/tpep/library/rainbow/index.html
(remove any spaces embedded in the URL)