Look no further, there is a script on PM written by tachyon here -> 115928 that does (similar to) what you want. You might need to tweak it a little bit to colour the exact difference.

Another off-the-shelf method I can think of is to use the package diff2html - 
diff2html file1 file2 > diff.html

[download]


In reply to Re: highlighting text changes by Roger
in thread highlighting text changes by cez

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