Thanks for your comments. The colors were added in the inital example just for marking the different 2.4GHz component seen. Of course there are no colors available in the terminal prg of the Arduino IDE.
The amount of power in each channel is displayed in ASCII grey scale. This is an old technique from the time when lineprinters were the primary output of mainframe computers. Have a try on your favorite search engine to find out more (here's one link which came up http://paulbourke.net/dataformats/asciiart/
There is no reason why the code should not work with current Arduinos as the code uses only standards. I have however no way of testing the UNO or newer devices - I do not own any of these.
In case you have doubts, try any of the newer RF24-libraries. Most of them feature a scanner example based on my old code. These libraries are pretty much up-to-date.
In any case - have fun!