An electromechanical linear oscillator with a random ambient excitation and telegraphic noise parametric excitation is considered as an energy harvester model. It is shown that a parametric colored excitation can have a dramatic effect on the enhancement of the energy harvesting. A close relation with mean-square stability of the oscillator is established. Four sources of the ambient excitation are considered: the white noise, the Ornstein–Uhlenbeck noise, the harmonic noise and the periodic function. Analytical expressions for stationary electrical net mean power are presented for all the considered cases, confirming the proposed approach.