This is really helpful Interceptor; many thanks for that link.
I also found this on a review site http://www.imaging-resource.com/PRODS/sony-rx100/sony-rx100VIDEO.HTM
" White balance settings also carry over to video mode, as do the tone/color aspects of the camera's various scene modes."
I've found that the 'AutoWB" and other WB settings have overrides (if you move 'down' with the joystick on the WB option) and you can shift the Auto (eg) towards red, blue or whatever you need. There is a full spectum color chart that you can move around and then set, and the color in the viewfinder shifts as you track across VIBGYOR etc.
If indeed the still WB settings carry over to video I believe there are more than enough options to play with, and to avoid using a red filter.
I'll report back once I've had time to play with the new toy.
Now I'm a little fellah, but even my fingers are like a bunch of bananas playing with this little gem. The u/w housing makes it more 'normal' sized lol. About the size of my old Nikonos II and III. Great construction, though the onboard strobe looks a little flimsy, just as well it is protected inside the aluminum housing when one is diving.