RAID5 Utility Shows Prefailure but no failure light on drive.

I have an Xserver (Late 2009) that has the 3 internal bays setup with 2TB drives each in a RAID5 array. (Plus an external 16TB RAID Array as well.) The RAID Utility shows that Bay 2 his a drive in a prefailure state. However, the light on the drive itself is green, not orange or red, as I might expect. The server is still up and operational. I have a replacement 2TB drive in hand to swap it out. However, I'm concerned that my drive light is green instead of orange/yellow or red to guide me to the failing hardware so I can replace it and begin the automatic rebuild process.

Any insight on what I'm seeing here?

Thanks!

Here's what the server drive bays look like:

And this is what my RAID Utility shows: