Focal Plane Ambiguity (FPA) is a fundamental limitation of the Depth from Defocus (DFD) technique and refers to ambiguity of two possible distances corresponding to a single defocus blur value. Since, mix-sided scenes exist frequently in images and image-sequences, the assumption of a one sided focused scene often does not hold true. This leads to errors in the estimated defocus map. However, the inherent ordering of defocus blurs at the edges due to chromatic aberration in the R, G and B color planes can be used to correct this ambiguity. But, in highly defocused regions the ordering of defocus blurs becomes unreliable as the detection of edges becomes erroneous. In this paper, we propose a novel region based method using Color Uniformity Principle (CUP) for detecting the ordering of defocus blurs in R, G and B color planes to resolve the FPA. © 2018 IEEE.