The two liquids are meant to not only add colour to the stew but also soften the meat. Dredging the cubes beef in flour is also key to a dark stew; the 3rd picture shows deglazed liquid after frying the beef pieces. I still need to experiment the recipe but feel free to replace your processed beef broth with some instant coffee (about 3-4 tbsp in 1L water for 1kg if beef) and balsamic vinegar (about 1-2 tbsp). The coffee did give a bitter aftertaste initially but trust the process! Keep cooking and you’ll be rewarded with a flavourful dark stew.