Bio:::Graphics is a namespace for a set of modules used for drawing images common to Bioinformatics. On my machine it's located in the directory /usr/local/lib/perl5/site_perl/5.8.6/Bio/Graphics
You could poke around there (or somewhere similar) if you'd like a peek at the source code. Probably the most reasonable thing to do would be to e-mail the Bioperl mailing list (there's a link off the website) and tell them your problem. Also, you might try some of the later examples in the tutorial and see if those work for you.
I ran the example using both sets of code and got the image with labels on it, so I don't know what the problem would be. What OS and Bioperl version are you using? Bioperl makes heavy use of the GD Perl package, what version of GD are you using?