Recent research has demonstrated that using low precision inside some levels of an algebraic multigrid (AMG) solver can improve performance without negatively impacting the AMG quality. In this paper, we build upon previous research and implement an AMG that can use double, single, and half precision for the distinct multigrid levels. The implementation is platform-portable across GPU architectures from AMD, Intel, and NVIDIA. In an experimental analysis, we demonstrate that the use of half precision can be a viable option in multigrid. We evaluate the performance of different AMG configurations and demonstrate that mixed precision AMG can provide runtime savings compared to a double precision AMG.