This works, (don't know about get_hotspot, where do you come up with that?)

#!/usr/bin/perl
use strict;
use warnings;
use GD::Graph::bars3d;

# sample data
my @data = (30, 45, 36, 42, 40, 44, 41, 39, 35, 46, 43, 38);
my @dt = ('2002-10-10 00:00:00', '2002-10-10 01:00:00', '2002-10-10 02
+:00:00',
'2002-10-10 03:00:00', '2002-10-10 04:00:00', '2002-10-10 05:00:00',
'2002-10-10 06:00:00', '2002-10-10 07:00:00', '2002-10-10 08:00:00',
'2002-10-10 09:00:00', '2002-10-10 10:00:00', '2002-10-10 11:00:00');

# setup the color set
my @colors;
for my $datum (@data) {
push(@colors, get_color($datum));
}

# create the data set for the graph
my @dataset = (\@dt, \@data);

# create the new graph
my $graph = GD::Graph::bars3d->new( 400, 300 );

# setup the graph options
$graph->set(
transparent       => '0',
bgclr             => 'lgray',
boxclr            => 'white',
fgclr             => 'white',
x_label           => 'Date / Time',
y_label           => 'Number of Woozles Sold',
title             => 'World Wide Woozle Sales',
dclrs             => \@colors,
cycle_clrs        => 1, # this is mandatory for this to work
x_labels_vertical => 1,
);

# plot the graph
my $gd = $graph->plot(\@dataset);

# create a PNG file of the graph
open(IMG, ">$0.png") or die $!;
binmode IMG;
print IMG $gd->png;

# returns the color name based on the value given
# this is only an example
# you should base your numbers off of your actual data
sub get_color {
my $value = shift;
return "dpurple" if ($value < 34);
return "lpurple" if ($value < 36);
return "blue" if ($value < 38);
return "green" if ($value < 40);
return "yellow" if ($value < 42);
return "orange" if ($value < 44);
return "red";
}
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