The Union Jack ring for the lovers of all things British. Comes in a single material, but you can fill it with some polymer clay, and voila, a custom colored Union Jack.
I've used some Staedlter Fimo clay for this(easy to get in France). I've filled all the gap with it, making sure every bit was properly filled. I was pretty messy about it since I was going to sand the exess clay in the end, it didn't have to be perfect. Baked the ring for ten minutes at 150°celcius (only get metal rings if you plan on doing this, since plastics will likely warp or melt in the oven). I've let it cooldown and then sanded it down. I'd recommend getting the raw materials for this, since you'll end up sanding it down. I'll probably sand it down and polish it to make it perfect.