J−H colour as a function of absolute J-band magnitude. Left: isochrones from chemical equilibrium models of this work (blue), B03 (orange), and SM08 (green). Right: isochrones from chemical equilibrium models (blue) and non-equilibrium chemistry models with weak (purple) and strong (red) vertical mixing from this work. In both panels the photometry of field brown dwarfs are plotted as black circles, with the data taken from the database of ultracool parallaxes. The data is filtered to only include field brown dwarfs from Dupuy & Liu (2012) and Dupuy & Kraus (2013).