BLOCK3:                     # 18 = (6 "diluted" hues) * (3 shades)
for my $h ( 0 .. $#hues ) {
    for my $s ( 1 ..$#shades - 1 ) {
        $dest-> colorAllocate(
            map { ( 1 + $s * ( $_ - 1 ) / $#shades ) * 255 } 
                ( 0 <= $h <= 1 || $h == 5 ),                # R
                ( 1 <= $h <= 3 ),                           # G
                ( 3 <= $h <= 5 )                            # B
        );
        push @chars, colored( $shades[ $s ], "$hues[ $h ] on_white" )
    }
}