In this thesis I study a two dimensional system of patchy colloids restricted to closest packing and its phase transition from an orientationally ordered into a disordered phase. I approached this problem by first defining orientational order by determining bonding patterns that emerge at low temperatures for different sizes of the patch. As the temperature is increased bonds start to break and this transition is studied via a suitable order parameter. The systems were investigated via Monte-Carlo simulations. In order to identify the emerging bonding structures, a density and a cluster size analysis were employed. For the case where particles can form up to one bond (dimers), an order parameter was defined. With this order parameter at hand a correlation function was defined and was calculated for different temperatures in order to study the spatial range of the order in different phases.