Did I mess this up?

I'll start off by saying that I'm new to this and this is going to be my second batch of beer (Fat Tire Clone). I ordered the Wyeast American Ale II 1272 from my LHBS and made a starter wort following the ratio of 3/4 cup light DME to 2 cups of water and boiling for 15 minutes. I pitched the yeast on Thursday night and doubled the starter yesterday morning shaking every few hours to give it some oxygen. This morning I put the starter in the fridge with the intention of leaving it there for 24 hrs and brewing the beer tomorrow. Everything seemed to look great, it had a nice caramel milky color to it, and the yeast layer on the bottom looked fine until I checked on it about an hour ago. There was a dark almost gray layer that had formed. Did I screw something up.

Looks just like its supposed too. The bottom layer is more compact and has less liquid in it, thus the lighter color, as the top layer compacts, it too will get lighter. No problems

Mmm looks good to me!