Hello mate,
I brought my gun here before I had my ukara registration. I two-toned it (painted a spare stock and front set bright green) and also brought the normal parts. Then on site I switched them before the game, and then back after the game. That is the legal way to do it. After the 3 games I got the ukara registration and got the rest of the guns shipped here.
Each time I wrote a letter about the guns (what it is, why is it green/why not, etc), and my contact details and put it in the package.