Grass discoloration

[eric317]

Hello all,
I'm new to the forum, so be gentle. Anyway, I put in sod at the end of March. It looked great at first. I gave it plenty of water and it took root just fine. But about two weeks ago, I noticed there were patches of darker grass becoming visible. It's almost a bluish/green in some light. Also, the blades of that grass seem to be thinner than the blades of the other. It's been mowed once just before I noticed the discoloration and I just mowed it again. It's not getting cut too short, I'm sure of that. Could it be a different species intermixed? It didn't look different when we laid it. It's been fertilized once. Any comments or suggestions? Thanks.