Multiple sensors image fusion is increasingly being employed in video surveillance. This paper presents a color based grayscale-fused image enhancement algorithm. The main advantage of this algorithm is to stand out meaningful information of a certain sensor in selected band of the color space, while maintain the high resolution of the grayscale-fused image. Moreover, a performance evaluation method based on analyzing the average gradients of the color-fused image is presented and experiments are performed using images under complex environment. The results show that the addition of color to grayscale-fused image can significantly increase observer?s sensitivity and the accuracy of further classification and recognition.