Preheat the oven to 350 F. In a medium bowl, whisk together flour, cocoa powder, salt, and baking soda.
In a large bowl, combine butter with granulated sugar and brown sugar until fluffy. Add in egg and vanilla extract, mix until smooth. Add in the flour mixture, and mix until it is fully combined.
Add in red food coloring, and mix until it is fully red. Use a cookie scoop to place cookies onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes.
Decorate the cookies with the pretzels, chocolate chips, and m&ms.
