In a large mixing bowl, combine flour, sugar, instant yeast, and salt. Gradually pour in lukewarm water while mixing to form a cohesive dough.

Turn the dough onto a lightly floured surface and knead for about 8-10 minutes until smooth and elastic.

Divide the kneaded dough into two equal portions. Add red and black gel food coloring to each portion and knead until colors are well incorporated.

Roll out each colored dough section into long strips, twist them together to form a swirl pattern, then shape into a loaf.

Place the shaped loaf into a greased loaf pan. Cover with a kitchen towel and let it rise until doubled, about 1 hour.

Preheat the oven to 350°F (175°C). Bake the loaf for 25-30 minutes until golden brown and sounds hollow when tapped.

Let the loaf cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.