On a PC, apparently you can double click a look file and its automatically registered.

On a Mac, you cannot do this. First Light also does not import of open a look file.

How can this be done on a Mac ?

Open .look files directly into FirstLight on the Mac to register them. I know this is how it works, but I do is so rarely as I use dropbox to share looks between my PCs and Macs. Using dropbox for this here vimeo.com/10024749

Hi David. If you are suggesting starting First Light, then Open -> .look

It does not work, the look files (and the clook) files are greyed out in the file selection window.

They are greyed out even when I try to import.

Could you explain how you "open" the look files on a mac ?

You can drag the .look files onto the First Light icon in the dock. That installs them as well.