Ah Yes, the 1/100 Justice...what can I say, this is the other model besides the Freedom that you should build with great care, the finishing product is amazing, you'll want to keep it in a glass case and cherish it forever. It's not too hard to paint either! You can grab the paint you need from the paint section if you need to. Justice is originally built by ZAFT and piloted by Athrun Zala. Its backpack, the "Sub-flight System," is actually a support vehicle that houses a set of cannons on top and can detach and fly on its own. Like the Freedom Gundam, it is equipped with a Neutron Jammer Canceler, allowing a nuclear reactor to be used for the powerplant instead of a mere battery. This means that the Justice Gundam can operate its Phase Shift system indefinitely.
For best results, paint the body red and strengthen the joints with putty.