I'm just guessing, but maybe:

While it might make some difference which version of Word you're using now, the problem you're seeing can show up due to the "Autocheck Grammar and Spelling" settings. The colored type indicates that the program thinks your documents include "errors."

It's also possible, though, to be while you're in "Compare Documents" (Compare versions in some Word versions?) mode, and the different colors are needed to show you which text comes from one document and which is from the other one you're comparing it to. (Word has never been too clear about which document is which.) If you "accept" or "reject" each bit of colored text, the "final" version shouldn't have the colors. There should be an "Accept All" or "Reject All" button but I can't tell you whether the colors are what will be saved or what will be deleted for a general case.

I don't recall where the settings were in older versions of Word, but in Word 2007 you need to check settings on the "Review" tab. Possibly just turning off "Track Changes" will solve the problem. The place to fix it should be easier to find in older Word versions - my memory just isn't quite that good.

If it's coming from the change tracking, it really is a useful "feature" sometimes, but has always been a confusing one for most people who don't use it frequently.

John