I've spent a lot of time on this because the most popular solution didn't work, and now that I figured it out, I want to post it so that, maybe, I help someone with the same problem as I had.
To change the cursor color on emacs depending if you are or not in god mode you put the following code into your init.el file.
(defun hook-update-cursor ()
(cond ((or (bound-and-true-p god-mode)
(bound-and-true-p god-global-mode))
(set-cursor-color "lime green"))
(t (set-cursor-color "cornflower blue"))))
(add-hook 'buffer-list-update-hook 'hook-update-cursor)
If that doesn't work, try this other one.
(defun my-god-mode-update-cursor ()
(cond
(god-local-mode
(set-cursor-color "lime green"))
(t (set-cursor-color "cornflower blue"))))
(add-hook 'post-command-hook 'my-god-mode-update-cursor)
The latter works for me, while the first doesn't.
I hope I helped!!!!