Combined color imaging with phase shifting, a technique named five-step color phase shifting (CPST) is presented to determine principal direction angle and the whole-field single isoclinic phase map in the range of [0,π/2]. A digital camera recorded five isoclinic color images coupled with isochromatics from a plane polariscope with five different settings, respectively. The unloaded light intensity image is introduced to operation. For knowing the accuracy of the CPST influenced by the different error sources, such as measuring intensities errors, orientation errors, and especially the initial stress errors, methods are given to analyze and estimate the influence of the different error sources on the final calculated isoclinic results. Experiments have been carried out with the simulation of a circular disk under diametral compression and some actual applications. This technique utilizes white light, which avoids undefined isoclinics near the locations where the isochromatics exist, and will have active effect on experimental stress analysis and structural strength design.