It is both color and alpha. I initially thought it was the material that I was using for the sprite that I am attaching, but that doesn't seem to be the case. Is there some code example on how to do this you could post so that I can make sure I'm doing it correctly? I've resorted to using skins in the meantime, but I think that, as my attachment option list grows, doing it this way might be more efficient.
Also, looking at the goblins example, those attachments are already part of the spine file, correct? I'm attempting to take a sprite from unity and attach it to the slot in the spine skeleton.