For your door I would....
(Or u can go with black instead of the blood look)
Plastic page dividers/page protectors
Magnets or tape
Mix your red & blue paint to the exact color of blood you would like...then add equal amounts of glue.
Using your protector sheets (I cut mine apart for more pages) smear your glue concoction on the sheet forming the letter of your choosing. Let dry and repeat (I taped my sheets to the patio door so they would drip too...just keep an eye on it so it doesn't get too messy). Once dry, cut plastic sheeting around each letter (leave a slight halo so the cling stays better). I removed mine from the plastic and just hung them with painters tape. But the plastic will add to stability with wind...use magnets or tape to install.