Red Giant Software has been kind enough to give the steps required to get back to FCP 5.1.2…including linking to the FCP 5.1.2 update package.

Going Back to FCP 5.1.2

I did this with success (thanks guys) and am in the process of trying to install Colorista again, but it isn’t taking. I tried installing 4 times and it still doesn’t show up in the EFFECTS>MAGIC BULLET folder.

Still trying…in their support pages now, which is where I found the link.