Step One:
Start with a completely black eye socket. If you primed your Marine a color other then black (i.e. Ultramarines Blue) you will need to blacken in the eye socket…but you should have primed it black in the first place!
In the following steps you will want to ensure to leave a black border around the rim of the eye. This will make the eye stand out.
Step Two:
Paint the lower front half of the eye red. While leaving the upper back half black. The lower edge of the red forms a curve that follows the edge of the eye socket, but leaves a line of black between the red of the eye and the green of the helmet as mentioned in Step One.
Step Three:
Along the front lower edge of the red that you painted in the last step, you need to apply a thin line of orange. The red is still the primary color of the eye. The orange is there to add a 3D effect similar to painting gems, so don’t go overboard and paint over too much of the red. Again, there should be a clearly defined black boundary between the orange on the eye and the green on the helmet.
Step Four:
The last thing to do is add a small dot of white to the back corner of the eye. This looks like light reflecting off the lens and gives it a glassy look.
This technique is used for all Marine lenses regardless of color. Just replace the red and orange colors with the appropriate colors for your Marine. Just like gems, the colors that look the best for lenses are red, green, and blue. The lens color should stand out from the Marine’s armor color (no green lenses on a green Marine).