my %colorsets = (
   samn  => [ "#A5A5A5", "#84B594", "#84A5C6", "#DE6BA5" ],
   atari => [ "#00ff00", "#8fbc8f", "#ffcc00", "#000000", "#33cc00", "#330099", "#363636" ],
);

my $set = $ENV{QUERY_STRING};
my $colors = (defined $set and exists $colorsets{$set}) ?
    $colorsets{$set} : $colorsets{samn};
my $numcolors = @$colors;

for (0 .. $totcells) {
    my $cellcol = $colors->[ rand $numcolors ];
    # the rest as above
}