Oh ok so you don't really know but ya when you buy one you can two it's not random. When you're walking around the tower with the Spirit of the Vulture it stays purple. At some point during battle in the field it will change to blue for a duration of time. Don't hold on to those motes too long. You can always get some more and i hoe you don't get too upset as i would if the engram give you something you can only use for a different class.

Yeah, i guess youre right. I hope they make us customize the color we like for bonds. And after this week with xur, ill be sure to get a bond from the speaker! I wanted the king bond from the last refresh