I don't think the 3rd metaphor fits. rgb values still points to a single color, which maps back to a single value on a 0 -> 1 or red -> violet continuum. It's more apt to describe it like a multi channel audio mixer. Many different channels ("really into a specific topic", "freaks out at parties"), each with their own value (10%, 20%).
Metaphors often fail though, so it might just be best to say what we mean plainly.
> rgb values still points to a single color, which maps back to a single value on a 0 -> 1 or red -> violet continuum.
No, it doesn't. Wavelength is unidimensional, but color can mix many wavelengths, and RGB is a 3d color system which doesn't cover all combinations of visible light but does approximate the way most human vision works, and is therefore useful as a description for human-perceived colors (and more accurate than picking a single point on the unidimensional wavelength spectrum for that purpose.)
An RGB value points to a single color, but if R is "really into trains" and B is "repetitive behavior" and G is "susceptibility to sensory overload", then it's basically the same metaphor as a multi channel audio mixer, except understandable to a different (and likely bigger) pool of people.
It doesn't have to be exact, but it's counter productive when it is clearly and meaningfully incorrect though. That's the problem with the two dimensional [0,1] scale as well.
That's just the limits of it being a metaphor. Audio mixers also only have a finite number of channels, but are also much less familiar to most people.
Metaphors often fail though, so it might just be best to say what we mean plainly.