use warnings;
use strict;

my %hash;

while (<DATA>){
    chomp;
    my ($key, $val, $colour) = split;
    push @{ $hash{$key}{$val} }, $colour;
}

for my $k (keys %hash){
    for (keys %{ $hash{$k} }){
        my $colours = join ':', @{ $hash{$k}{$_} };
        print "$k $_ $colours\n";
    }
}

__DATA__
A1 abc yellow
B1 xyz green
A2 cde red
A1 abc green
A2 cde yellow
A1 abc blue

##</code><code>##

A1 abc yellow:green:blue
A2 cde red:yellow
B1 xyz green