This is an alternative technique to cook Brussels sprouts, using a pan instead of a pot and you can color the sprouts /similar to roasting/ by using dry heat and some olive oil, and then adding liquid in the second stage of cooking. The liquid can be a variety of materials depending on the end result you wish to achieve.
Browning as a result of heating, also known as the Maillard reaction starts at 140°C. The sugars and proteins, amino acids on food go through a series of chemical reactions requiring energy to create melanoidins. Melanoidins are large molecules made up of polymers that have a brown color but more importantly have attached flavor molecules.