I run into that all the time, because I use a black desktop background. (Although your problem may be caused elsewhere.) Try these extra settings: 
$graph->set(
             transparent       => '0',
             bgclr             => 'lgray',
             boxclr            => 'white',
             fgclr             => 'white',
             x_label           => 'X Label',
             y_label           => 'Y label',
             title             => 'Some simple graph',
             y_max_value       => 8,
             y_tick_number     => 8,
             y_label_skip      => 2
             ) or die $graph->error;

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I'm not really a human, but I play one on earth. flash japh

In reply to Re: GD Graph: gif comes out a large black rectangle. by zentara
in thread GD Graph: gif comes out a large black rectangle. by pmneve

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