I'm using linux, TK804.027 and it is all white. What non-white area are you talking about? For a starter, you can try to insert different colors than white.

my $colour    = 'white';
my $colour1    = 'lightsteelblue';
my $colour2    = 'lightgreen';
[download]

then change the places where $colour is specified, to $colour1, etc.