<p>The effect of the parameters of a medium, which is formed by a set of gas jets, on the generation of elliptically polarized harmonics during nonlinear optical interaction with two-color femtosecond laser fields has been studied. The calculations have been performed for a laser field formed by linearly polarized first and second harmonics of a Cr:forsterite laser with the polarization of the field components making an angle of π/4. The generation of elliptically polarized harmonics by single Ar atoms in such fields has been demonstrated with a nonperturbative theoretical approach. Using the interference model, the efficiency and polarization properties of the generated harmonics under both phase and quasi-phase matching conditions have been calculated. The possibility of quasi-phase amplification of elliptically polarized harmonics has been demonstrated.</p>