I made these eyeball gloves for a costume (see my beetlejuice instructable for the full Adam and Barbara Maitland costumes!) but they look nice without the glove for a fun or spooky Halloween accessory or prop :)

Step 1: What You'll Need

-foam balls (i recommend the dense foam ones, not the flakey Styrofoam ones, they are easier to paint and cut) I got twelve 1.5 inch balls at Jo Anne fabric for less than $3.

-paint (white, yellow, black, gold, and whatever color iris you want, I chose blue)

-paintbrushes (including a very skinny bristle for small details)

-paperclips (not necessary but helpful)

-skinny red sharpie pen

-clear coat glossy spray paint for protection

Step 2: Prepping the Foam Balls

in order to stabilize the balls and paint the entire surface, I unbent a paperclip and placed it inside the bottom of the ball (there was already a hole in these ones so I just pushed it in a bit further).
I gave them all a coat of white to try to fill in the small gaps that are in the foam. in order to dry without messing up the paint, I hung them from a cup rim with the other side of the bent paperclip :)

after I completed a coat of white, I mixed the smallest amount of yellow in and painted a 2nd coat in order to give an off-white color with a slight yellow tinge

Step 3: Painting the Iris

choose your color and place a nice sized circle on each ball. I let it dry and put a 2nd coat to darken the circle and fill in any splotchy areas

Step 4: Give Your Iris Dimension

in order to get a more realistic look, mix your iris color with a little bit of white to lighten it up and create a bursting star shape in your iris, almost extending to the outer edge of the iris. let that dry, add a bit more white to lighten it further, and do it again, but with smaller rays extending out so you are able to see all 3 shades of color

Step 5: Outline the Iris

mix a tiny bit of black with your original iris color and with a very skinny brush, make a ring along the outside of the iris. I went for the deepest blue I could but it still turned out more black than I had wanted :/

Step 6: Soften the Rim

next I took my brush with the original shade in the iris, and dabbed it around the inside of the outer rim. this softens the outline and gives a little more dimension to the iris

Step 7: Go for the Gold!

mix your gold with a bit of white and create another star burst in the iris on top of your previous layers. I made this one more of a spiky, condensed circle than previously, and I didn't extend quite so far to the rim.

after that dries, mix your gold with a bit of yellow and complete the process again. for this one, I did extend the rays a bit further and more spaced out so you can still see the variety of blues

Step 8: Paint the Pupil

after the gold dries, paint a solid black circle in the center of your eyeball for the pupil. after that dried, i placed a tiny white dab in the outline of the pupil to give the illusion of a light reflection.

at this point, you can also go back and make any touch ups in your other colors (i wanted to extend the lighter blues and golds a bit further outside the pupil on some of them to be more noticeable)

Step 9: Make the Blood Vessels

using a skinny red sharpie pen, I drew on my blood vessels starting at the bottoms and working my way toward the iris.

Step 10: Gloss and Protect!

I used a clear acrylic sealer to spray over the eyeballs. MAKE SURE TO DO THIS STEP OUTSIDE OR IN A WELL VENTILATED AREA!

Step 11: Optional: Make Them Bloody or Attached to Gloves!

my costume called for eyeballs as fingertips with goopy blood dripping, so I cut holes into the bottoms of them and attached them to the 10 fingers of a latex glove for easy donning/removal. I cut the holes by grinding a kitchen knife inside the eye, and marked the inside of each eyeball to remember which finger it was designed for.
using a wind chime pipe (the only semi-finger-shaped device I could think of) I pushed out the fingers of the glove, put hot glue inside the hole of the eyeball and stuck them on top of the latex gloves. (DO NOT DO THIS WITH YOUR HAND INSIDE) after it was sturdy and stuck, I overdid the glue on and around each eyeball to look like gooey blood dripping. after drying, I painted the glue red.

and voila!