Here's a rewrite of the colour correct applying script that I wrote a while back with a few improvements.
The new version of it keeps the diffuse colour of the material correctly so that if you don't have a texture in the diffuse of the material - it'll put the same diffuse colour into the colour correct map instead. It also has a default value of 2.2 which should save a bit of time. Lastly there's a remove colour correct button if you want to quickly convert a gamma based scene into non-gamma quickly.