On Aug 14, 2017, at 11:27 PM, Alan Third <alan@idiocy.org> wrote:

On Mon, Aug 14, 2017 at 05:47:12PM +0200, Artemio González López wrote:
After deleting the file ~/Library/Colors/Emacs.clr, everything went
back to normal. Thanks a lot for pointing me in the right direction!

I believe you need to delete the file every time you restart Emacs. We
don’t have any other work‐around for this at the moment as we don’t
know why it’s happening.
--
Alan Third

You’re right, Alan. Today Apple released a new beta; we’ll see if the issue persists.

Thanks again,

Artemio