We consider the instabilities of field perturbations around a homogeneous background color-electric and/or -magnetic field in SU(2) pure gauge theory. We investigate a number of distinct cases of background magnetic and electric fields, and we compute the dispersion relations in the linearized theory, identifying stable and unstable momentum modes. In the case of a net homogenous non-Abelian B field, we compute the nonlinear (quadratic and cubic) corrections to the equation of motion and quantify to what extent the instabilities are tempered by these nonlinearities. Published by the American Physical Society 2024