How to change the keys of a dictionary?

Let's say I have a pretty complex dictionary.

{'fruit':'orange','colors':{'dark':4,'light':5}}

Anyway, my objective is to scan every key in this complex multi-level dictionary. Then, append "abc" to the end of each key.

So that it will be:

{'fruitabc':'orange','colorsabc':{'darkabc':4,'lightabc':5}}

How would you do that?