Put the eggs in a small pot and cover with water over high heat.
Bring to a boil and boil for 5 minutes.
Turn off heat and let sit for 10 minutes.
Remove the eggs from the water. When cool enough, use a spoon to gently press on each egg to crack the shell.
In a bowl just large enough to fit the eggs, mix cold water and black food coloring until the water is dark.
Place the cracked eggs back into the water. Refrigerate for at least 2 hours or overnight.
Remove the eggs from the refrigerator and discard the water.
Carefully peel the eggs. Cut them in half lengthwise and scoop out the yolk, placing them in a bowl.
Add the mayonnaise, salt, and food coloring to the yolks. Use a fork to mash and combine.
Scoop the mixture into each egg half.
Chill until ready to serve.
To serve, garnish with black poppy seeds and plastic spiders, if desired.