A while ago I wrote a program to make two-column highlighted diffs on the command line:

I find it really useful, but many people who I think would feel similarly don't know about it. So I just made a small page describing it with screenshots etc: www.jefftk.com/icdiff.

(When I've made pages before with any amount of thought to mobile design I've just gone with a single column. This one is responsive: when your browser is wide enough it shows the two diff images side by side.)