There are multiple levels of processing here, so this pure trichromatic model turns out to be a somewhat misleading mental model to fix on. The signals from three types of cone cells are processed immediately within the eye into 3 different signals, a lightness response (L + M), a yellow-blue response (L + M – S), and a red-green response (L – M), before those combined signals go through further processing. LMS signals per se don't get sent anywhere further up the chain. If you are red-green colorblind that means you aren't getting much if any useful signal from the L – M response, either because your 'L' and 'M' cones are too close together to meaningfully distinguish, or because you are missing one of the two entirely.

[Calling the LMS cone types Short = 'blue', Medium = 'green', and Long = 'red' creates a lot of confusion. Stick to long/medium/short labels. A statement like 'there is no such thing as pure green' is nonsensical. As Newton figured out, light rays themselves are not colored; color is a higher-level percept constructed in the human brain. Green is no more or less 'pure' than blue or orange or purple.

For that matter calling the RGB primaries 'red', 'green', and 'blue' causes some confusion also, as these primaries are seen as an orangish red, a yellowish green, and a purplish blue, nowhere near the 'unique hues' red, green, or blue. E.g. the use of these names in named CSS colors, etc. is a horrible human interface.]

If you are interested in the details, this is one of the better sources online http://handprint.com/HP/WCL/color2.html [I would refer you to books but those are hard to accessibly hyperlink].

As for rods, their response is pretty much ignored during the day. They are much more sensitive, so start kicking in when the visual system adapts to very low levels of light where the cone cells aren't getting much useful signal.

The article under discussion in this thread is full of technicalities, and in a brief skim I didn't notice any obvious errors, but it ignores several of the most important high-level features of human color perception – and gets a bit confused about the relationship between color reproduction via additive RGB displays, color measurement by instruments, and models of human vision – and therefore isn't the most useful resource for someone new to the subject, IMO.