hello nanokiper, from your pic, I dun see any tissue. maybe I got a very bad eyes thus can't see clearly. attached some pic for u.
this is a dead sps, showing its skeleton after dry
u can see the veins(lines) underneath its coralite?? tissue is present.
this is a small green acro the tissue and veins(brown lines) is visible.
possiblity that the frag has been dead for sometime and algae start to grow thus giving the green colour. check it further for any tissue. Pls forgive me if i'm wrong.