That looks great, I especially like the eye! Is it air brushed?
Just layering :)
The fade from the yellow around the iris through the red and into the black is magnificent, I really like it!
The light colour around the pupil is actually off-white (VGC Bone White) :) I wanted to keep the colour palette limited to red/black-only for this model.
During priming, I did a quick spray of dead white (VGC) to the front of the eye to get the red around the pupil as bright as possible. I painted the inside of the eyelids off-white to give a slight glowing effect to the iris and feathered it out before layering the red.