You just use a external switch or trigger from the external video source i.e. a DVD player. I do supply the instructions.
As for the wiring colours, I have them if needed.
You do also have the option of a second video input for say - a reversing camera etc.
Wellcome to your worst nightmare. I also have a RX with the touch screen, trying for more than two years to find the meaning of the connectors. My idea was to ad a 3rd party video input to the screen, with no success at all. Even in Lexus does not have all the info about the screen. All manuals reach the "Change the screen" sentence when the problem involves the screen...
Anyway, this is the info I have. The screen has 4 connectors, one for the Sat-Nav CPU, another for radio-AA controls, and another for consumption computer. There is another on that should be free if your car does not have the RES. It is white with six pins. They should be ground, sync, red, green and blue. But which one is each one...no idea. Also, no idea about how to make the screen to change from nav or trip information to video input...
Some time ago Vais technology used to have the video interface, and iti s apity that they do not offer them anymore, because the Ipod one really works well.
In case you need wirign from audio, I have the documents. Ask me.
Good luck and in case you suceed, please email me...