A study on color edge detection using the improved Di Zenzo's gradient operator associated with quaternion Hardy filter is presented. The Di Zenzo gradient operator recently achieved great attentions in edge detection, but it is sensitive to image with additive noise. The quaternion Hardy filter demonstrates its advantage in denoising image. A robust color image edge detection algorithm called Quaternion Hardy filter with the improved Di Zenzo's gradient operator, namely QHFIDZ, is presented in this paper. It preprocesses the color image to quaternion Hardy filter which reduces the noise effect and then apply the improved Di Zenzo's gradient algorithm for edge map. The proposed technique is a robust algorithm for noisy image detection comparison to other image detection techniques.