Two-colour movies using a single filter?

A short movie from 1930, The Devil's Cabaret, popped up in my YT feed recently. It's an early-ish MGM talkie filmed in early-ish two-colour Technicolor. It's pre-code, well worth watching in its own right. Colour and sound are actually quite good. Anyway, it's prompted me to take another look at my old item on the Friese-Greene process, also in two colours.

Two things stand out:

First, each film frame in the former process is in 'full' colour, whereas each frame in the latter process is in a single colour, complementary to that of its neighbours and relies upon persistence of vision to achieve an impression only of colour, making it more of a curiosity, as it can't have been easy to watch at the time. (Luckily for us, the modern F-G digital print doesn't do this).

Second, was I really correct in saying that the camera used in the latter process had a red filter alternating with no filter at all? I made that statement having recently seen the TV programme, but now all I can see online is that Claude F-G used the same process (Biocolour) that his father had invented, with a camera using red and green filters alternately. I would have thought that two filters would have made it easier to provide good colour reproduction in the final print, as well as better mechanical balance for the camera. I'll just have to see if I can find The Lost World of Friese-Greene documentary...