use strict;

my %byColor;

while (<DATA>){
  my ($fruit, @colors) = split;
  for my $c(@colors){
     push @{ $byColor{$c} }, $fruit;
  }

}

for my $c(sort keys %byColor){
   print "$c\t @{$byColor{$c}}\n";
}
__DATA__
strawberry red green rose
apple red rose
mango green