Hmmm if you already have a 10 motif onyx, a 5 motif in onxy will give you the versatility of wearing it as a set (necklace and bracelet), as well as attach it as a longer necklace. I am not sure if it would look weird attaching another color. I was wondering that myself as I am considering either another 5 motif malachite to add to my existing 10 + 5 to make a 20, or perhaps a 5 motif MOP. I believe it may only work if you have long hair and wear your hair down most of the time? So that the different color stone is towards the back of your neck. It would be great to hear what the other experts have to say!