Abstract: Owing to its success in particle physics, Yang-Mills theory has received a surge of interest in cosmology, where theories of inflation have traditionally relied on scalar fields and their built-in isotropy. The realization that a cosmic triad of vector fields could also yield viable solutions has prompted further research into models based on non-Abelian symmetry groups to describe the expansion history of the Universe. In this work we investigate the cosmological implications of SU(2) gauge fields in the context of inflation and dark energy. When coupled to gravitational waves, gauge fields lead to the emergence of novel dynamics ranging from the modulation of their amplitude to acting like a birefringent medium for primordial gravitational waves. We further show how an axial-gravitational anomaly can arise and lead to a successful model of leptogenesis, thanks to the intrinsic handedness of non-Abelian gauge groups. These mechanisms are studied both in the case of single and multiple SU(2) gauge fields by taking advantage of higher dimensional group embedding. We calculate the effects that these vector gauge fields have on cosmological observables, including the detection of gravitational waves and their polarization pattern on the CMB.