Light, and therefore color, is a wave when it comes to how we sense it. Like sound, if you take to frequencies and add them together, you don't get an average. You get a more complex wave that produces a complex sound (a chord) somewhat akin to a secondary or tertiary color.
If you're talking about how we sense light, it's more of a vector of 3-4 scalar values. You have activation levels for your rods and each of your cones.
Light is physically a wave, but that's not especially relevant to how you sense it.
