RainbowPIV is a recent imaging technology proposed for time-resolved 3D-3C fluid velocity measurement using a single RGB camera. It dramatically simplifies the hardware setup and calibration procedures required compared to alternative 3D-3C measurement approaches. RainbowPIV combines optical design and tailored reconstruction algorithms, and earlier preliminary studies have demonstrated its ability to extract physically constrained fluid vector fields. This article addresses the issue of limited axial resolution, the major drawback of the original RainbowPIV system. We validate the new system with a direct, quantitative comparison to four-camera Tomo-PIV on experimental data. The reconstructed flow vectors of the two approaches exhibit a high degree of consistency, with the RainbowPIV results explicitly guaranteeing physical properties such as divergence free velocity fields for incompressible fluid flows.