Blood
Stuff you need: Sugar-one 4 or 5 pound bag; 2 to 3 bottles of red food coloring; powdered milk (smallest box you can find); a few drops each of blue and green food coloring (or one of those larger 16 oz bottles, in which case you'll have lots extra); jars or containers to store blood in; large saucepan; dishwashing liquid.
Pour some sugar into a large saucepan with about half a quart of water. Bring to a boil. Pour in ten ounces or so (about 2 1/2 to 3 bottles) of red food coloring. Dissolve as much sugar as possible.
Pour into containers and let sit until cool. Excess sugar will settle to bottom. Bring to a boil again.
Blood should be bright red and transparent. Add a few tablespoons of powdered milk at at a time, stir in well, until blood reaches desired opacity. Remove from heat.
Add about half a cup of dishwashing liquid (to aid in cleanup). Stir in.
Begin adding blue and/or green food coloring, one drop at a time, until the blood becomes a bit darker and duller.
Pour into jars and cool.

Cost

  • Sugar: $2
  • Food Coloring: About $6
  • Milk: $2
  • Dishwashing liquid: hopefully you have this anyway, so we won't count the cost.
So you'll end up spending about ten dollars (US) to make about 32 ounces of this blood. You'll probably have left-over ingredients, so the next batch will be cheaper.