I got my Grenade on release day and threw about 5 games with it on a very dry pair of lanes.  The ball would come back with no oil rings on it at all and the ball was great on that kind of condition.  
I read it somewhere about the bleeding of urethane balls, but why does this happen?  The ball was brand new, threw only a few games on dry lanes, I still wiped the ball before every throw (part of the preshot routine thing) and went home and cleaned it with a cleaner.  The next day I pulled the ball out of my bag and it looked like it was covered with oil.  So I cleaned it again with the cleaner and put it back in the bag.  A couple days later I checked it again it it was again covered with oil, so again, I cleaned it.  Today, same thing.  
So, being that I threw this ball for only a few games on dry lanes, is this oil that was actually sucked up or is this something in the urethane or something totally different?  

Thanks for the replies guys.  Ok, so it's bleeding color pigment. I thought it was some kind of oil because it felt kind of slippery like light oil, and when I clean the ball, there is no blue on the towel.