@Dave: I do want to learn more about how the cone sensitivity graphs translate to actual nerves firing. I agree that's a key missing piece to this story. Please do share if you have articles or resources for that!

The Philosophy of Color course was great. We talked a lot about the qualia of a color - that is, what it's like to see something as red - and how to know whether others experience red the same way we do. And yes, we did talk about whether a red object is still red when the lights are off. Is it even always red when the lights are on? Don't forget the dress: https://en.wikipedia.org/wiki/The_dress (The Wikipedia article does a great job explaining how how our assumed lighting conditions dictate the colors we think are in the dress.)