You could do a manuall pixel by pixel count of the color, like in

#!/usr/bin/perl
use warnings;
use strict;
use Image::Magick;

my $file = shift or die "Need a file $!\n";

my $img = Image::Magick->new;
$img->ReadImage($file);

# if you want a pixel by pixel list of every color
# a huge slow output
#$img->Set(magick => 'txt');
#$img->Write("$0.txt");

#histogram
#returned values are an array of 
#red, green, blue, opacity, and count values.

my $tot = 0;
my (@colors) = $img->Histogram();

#print join "\n\n", @colors;

while (1){
     if (scalar @colors == 0){last}
     my $r = shift @colors;
     my $g = shift @colors;
     my $b = shift @colors;
     my $o = shift @colors;
     my $count = shift @colors; 
     $tot++;

        my $rh = sprintf('%02X',$r);
        my $gh = sprintf('%02X',$g);
        my $bh = sprintf('%02X',$b);

print "$count ($rh,$gh,$bh) at $o opacity\n"; 
}

print "\n$tot total colors\n";
[download]

You could then setup suspicious range ranges of colors, and do whatever.

Also google for "ImageMagick flesh color detection" for many other ideas.