LatexDiff is a great tool to generate colored diff file (as for Ms Word for instance) if you want to highlight only the differences.
Here’s how to use it :
latexdiff versionA.tex versionB.tex > versionDiff.tex
It’s not just a text diff as it generates an actual latex file. You just build it and you’re good to go.
Also, if you’ve read my post on Git+Latex, I’ve made a little wrapper to invoke latexdiff directly on git commits. Here’s the source code: