We report the EPR observation of two different color centers due to N2− molecular ions. The signals observed between 4 and 120K are attributed to an N2− ion substituting for two chlorines. The model is very similar to the O2− ions in the same matrix. Above 120K, thermally activated processes induce a spin-lattice relaxation and smear out the spectra. A simple technique is proposed to measure the activation energy of the reorientation.