Yupp they do, same way as with roids.
The one I popped earlier was slightly darker than a regular hulk and looked to have a bit of red color in it, first I was thinking it somehow was the light in the sector that changed the color slightly but when I mined it it went poooof.
I notice the above lvl 2 one is green and easily spotted. so different one from teh one I had. Maybe they change with hulk level?