#!/usr/bin/perl -Twl
use strict;

my @SAFE = qw(0 51 102 153 204 255);
my @RGB = ([RED => 0], [GREEN => 1], [BLUE => 2]);

sub get_set {grep { $_ >= $_[0] && $_ < $_[1] } @SAFE}

sub dec_hex {map {sprintf "%02x", $_} @_}

sub permute {
    my $last = pop @_;
    return map [$_], @$last if(!@_);
    return map {
        my $left = $_;
        map [@$left, $_], @$last
    } permute(@_);
}

foreach my $R (@RGB) {
    print $/, $R->[0], 'ish:';
    foreach my $t (get_set(51, 256)) {
        my @clrs = get_set(0, $t);
        foreach (permute(\@clrs, \@clrs)) {
            my @tuple = @$_;
            splice(@tuple, $R->[1], 0, $t);
            print '#', dec_hex(@tuple);
        }
    }
}

print $/, 'GRAYish:';
print '#', dec_hex(($_)x3) for @SAFE;