I tried Quantum::Superpositions for this - and it seems to work fine:

#!/usr/bin/perl

use strict;
use warnings;

use Quantum::Superpositions;
use Data::Dumper;

my %colors = ( red => '#ff0000', blue => '#0000ff', 
               green => '#00ff00', yellow => '#ffff00', );

my @sel_col = qw/ red green /;
my @missing = eigenstates((any keys %colors) ne (all @sel_col)); 
print Dumper \@missing;
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