Mixing red, green, and blue light can produce almost all colors the human eye can see. The wavelengths and frequencies are only to-scale relative to each other, and the time is not to scale at all. Three effects are visible: interference and group velocity. Interference comes in two types, constructive (1 + 1 > 1) and destructive (1 - 1 < 1) and is literally just adding the waves. Group velocity happens because of interference, making “wave packets”, and it can be more, equal to, or less than the actual wave’s speed. The last one is trichromacy. There are a near-infinite amount of wavelengths for light, however our eyes have only 4 (sometimes 5, 3, 2, or 1) light detectors. One of them is rods, which are mainly for brightness and only really matter in the dark, and the 3 remaining ones are the cones. They are sensitive to different wavelengths: long cones sense ≈560 nm, medium cones sense ≈530 nm, and short cones sense ≈430 nm. Signals from these cones are mixed together to form an image. A 600 nm photon and a 400 nm photon, even when mixed together and in the same direction, will activate both the L and S cones, allowing us to just make both appear very close to each other. This is what an RGB display (like your screen) does It is of note that M cones never activate alone: they are so close to L cones in their peak that they actually overlap, meaning that all green you see is technically not fully saturated, unless only the M cones are activated (ex. if the L cones get fatigued after staring at red for too long).
