If you are willing to use other modules instead of GD you could also use Imager. It is easier to install than Image::Magick, and it is capable to do many image manipulation stuff as well.
It also has gif support, if you need that. It will ask if gif support should be enabled during the installation.
For setting the hue and saturation of the image do this:

my $color = Imager::Color->new(hue=>120, value=>1, saturation=>0.5);
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