Disk not mounting after enabling TRIM
Don't panic! I hope you haven't done irreparable damage with the disk utilities and partitioning, which has nothing to do with the problem. The fix is actually very simple.

The grey screen is caused by the non-signed kernel driver for the SSD. Mac OS X won't allow it to load by default, thus you can't access the boot disk.

This can happen if you don't turn off the kernel signing check, or if it gets turned on, which it often does during a system update.

If you are using Trim Enabler, this article describes how to recover. A similar procedure should work for anything that turned on trim. 

I'm using a Crucial SSD too, with trim enabled. I forgot to turn Trim off before a system update, and had to recover using the instructions on the linked page (successfully).

Basically it overrides the kernel signing check once again, so you can boot your Mac like before.

https://www.cindori.org/trim-enabler-and-yosemite/

Once I was back in, I used the trimforce command to prevent the problem in the future ;-) Trimforce is new in Yosemite, I believe.