How can I highlight different parts in the Mac OS X Terminal app? For example a different color for input and output? Are the pre-defined color themes I can activate/download?
This answer explains how to configure the colors used by your Terminal profiles (e.g. a Futurama based color scheme) and how to enable color output for selected commands.
You can easily adapt this answer to make only your command input colored by applying what is explained in this post's section Colors instead of making text bold.
A great way to get basic syntax highlighting on your console is to install fishfish. It offers basic syntax highlighting and much more.
Here is a screenshot of how it looks like: