This paper concerns time synchronization of MIMO systems. The current most powerful receiver is a generalized likelihood ratio test (GLRT) receiver, and assumes unknown, stationary, circular, and spatially colored Gaussian noise. However, this receiver is more complex than its non-GLRT counterparts, which, unfortunately, do not perform as well in most cases. As the complexity is an important issue for practical implementations and may be prohibitive for a large number of antennas, the purpose of this paper is to propose several ways of decreasing the complexity of the GLRT receiver while keeping its performance. Simplifications of the GLRT receiver and optimization of parameters, jointly with new low-complexity receivers, are introduced. The performance of the new receivers is analyzed and compared with that of the GLRT receiver, enlightening the practical interest of these receivers.