About elincia s and Ryoma s shurikens..

I'm not sure yet, but people have speculated that you should be able to inherit the daggers seeing as you can inherit different color dragons different colored breaths. And the character should keep their original color.

They should change color depending on the character wielding them. I have Fishie Bow on Legendary Lyn and it counts as green because she's wielding it. So the daggers should work in the same way.