Begin by greasing a baking sheet or marble slab with butter or cooking spray to prevent the taffy from sticking.
In a large saucepan, combine the sugar, corn syrup, water, and salt. Stir the mixture over medium heat until the sugar dissolves.
Attach the candy thermometer to the pan and continue cooking without stirring until the mixture reaches the soft-ball stage (around 240°F or 115°C).
Once the mixture reaches the desired temperature, remove the saucepan from heat and stir in the vanilla extract and food coloring if desired.
Carefully pour the hot mixture onto the greased surface. Allow it to cool for a few minutes until it's safe to handle.
Once cool enough, generously butter your hands and begin to stretch and pull the taffy. Continue pulling until it becomes light and fluffy, about 10-15 minutes.
Once the taffy has reached the desired texture, form it into a long rope about 1 inch thick.
Use kitchen scissors to cut the taffy into bite-sized pieces and wrap each piece in wax paper.
Store the wrapped taffy in an airtight container at room temperature.