Note that if you're an Emacs user and you execute commands from inside Emacs, there is already a framework for colorization in the fontify-* or highlight-* functions.
Each phone could have a built in key for signing. You could tell operators to not allow any other phone except for yours (which has this key) to access your account. Not a problem.
Tried most of the non-Apple Terminal alternatives, but personally I have always kept returning to Terminal because there is something about its finishing touches that add up.