Why does Mac change image file name?

Apologies if this has been asked before; I did a search (Google too) and can't find an answer to this question...

I have used the menu in my 7D to change the file name prefix to any number of custom names, for example, "7DEG" and then the camera will add the sequential file number.

But when I put the CF card in the reader and look at the files on my Mac prior to import, my Mac changes the first character of the file name to an underscore "_". This carries through when imported to Lightroom.

So for example, if I set up the file name in the 7D to "ABCD+file sequence number," it shows up in the Mac finder as "_BCD+file sequence number."

Any idea why the Mac is doing this, and how to prevent it? I know I can do a batch renaming of files, but that's one more unnecessary step when I am trying to streamline things. Thanks in advance....

The underscore denotes you are using Adobe RGB color space instead of sRGB...

From the manual:

Thanks mguffin!

This even applies to RAW files that actually have no colour profile untill processed in a RAW converter, if the colour space is set to AdobeRGB. It will of course affect the colour of the preview JPEG embedded in the RAW though.

Alan