Electromagnetic radiation of PC contains video information, and the image can be reconstructed. It is well known after the Van Eck's paper. The video cable used to connect the display with the graphics controller turned out to be the primary source of the leaking signal. For digital video interface, not all kinds of color images can be intercepted and reconstructed. Firstly we analyzed which color image can be reconstructed based the digital interface standards. Then we propose a method that changes the original PGB signals to safety color, while keeping the quality of the image by using the characteristics of the human visual and color mixing. By implementing this method on FPGA board in an ordinary computer system, we confirmed the effectiveness of our method as a countermeasure for the electromagnetic video information leakage. 2016 IEEE.