Bill -

Iodide will give sensitivity in the green with dry plate emulsions. According to Mees and James (1966), silver bromide is sensitive to 490 nm and silver bromide with 3% silver iodide is sensitive to 520 nm. According to NASA
green has a wavelength of about 510 nm.

As far as red sensitivity, I'd be interested in seeing his evidence of that. I understand that James Clerk Maxwell made the first color photo using blue, green and red filtered exposures, making reversal transparencies, and then projecting them back through the red and green filters. I can't find a reference, but I understand that he used an exceeding long exposure to make the red exposure. If you look at the graphs of spectral sensitivity of the different silver halides, I wonder if the "practical" sensitivity can be extended via filtration and long exposure...