* Both of these ideas are all over the internet, and I found out about them when my color-changing martini appeared on various "Creepy Halloween Foods" lists (dabbled, neatorama, mentalfloss, etc). I concede that it does have a certain mad scientist vibe to it, but it's hardly gross or scary!
Step 1: Ingredients
For the bloody eyeball cocktail:
Lychees, canned and peeled in a can
Cranberries (fresh or dried)
Dry ice is optional for both, but makes for a great creepy effect - and of course very effectively chills the drink.