
Mainly a colour edit. Make sure you get maximum use out of your values for stuff like this.
You had your values like this:
0, 19, 50, 100
This limits where they can be used and what combinations they can be placed in, you're better off with this:
0, 33, 66, 100.
Main thing to avoid is creating any banding. The top of the eye is a particularly prominent case.