RGB (Red, Green, Blue) is an analog video cable. It is only component video, no audio. A red white yellow cable is composite audio (red, white being the left and right signal and yellow being the video signal. An HDMI cable would have HDMI connectors on both sides and the signals are both stereo audio and component video signals. The HDMI is a digital signal where as the red green yellow are analog signals so you would need something to convert the digital to analog, so there is no "cable" that is HDMI to red, white yellow.