We demonstrate a simple and effective method for assembling ring-shaped colloidal structures by application of a uniform magnetic field to a solution of colloidal particles of various sizes and magnetizations. Initial studies employed 2.7-um paramagnetic beads, 1-um non-magnetic polystyrene beads, and a fluid dispersion of 10-nm iron oxide nanoparticles (i.e., ferrofluid). The ferrofluid serves as a magnetic contrast medium to adjust the relative magnetization of the colloidal components. The paramagnetic and non-magnetic beads appear positively and negatively magnetized with respect to the surrounding fluid. The induced dipole moments lead to the formation of ring-shaped colloidal assemblies as opposed to the chain-like structures commonly observed in mono-component colloidal systems. We also demonstrate the formation of more complex flower shaped colloidal structures by using multiple different bead types. This technique is a universally applicable self-assembly methodology, due to its insensitivity to the composition of the non-magnetic components.