Interestingly, the whole question of what is a "chair", what is "blue" and what is "pain" is sort of what Popper was on about. Note that my comments below rest on the notion that we're kind of stuck using words we know to communicate concepts, whether novel or not. I am going to try and integrate the whole public/private language discussion here as well, but no promises that I'll do it well.
Soooo...Popper says that there are three worlds -- the concept, how we measure (or describe) that concept, and what is in the real world. In the case of the color we call "blue", we would take Popper's framework and apply it this way: In an effort to develop our *best* definition of the color "blue" (the concept), we would show a lot of people a lot of different colored items, say pieces of paper, or objects found in nature (how Aristotelian of us) which represent what is in the real world. Perhaps we'd start with a bunch of stuff that was sort of blue, maybe some greens and purples that are on the blue side. This would be an a priori selection of items, and sometimes we want to do this if we already have a good base to work from (a more public language already established for the concept?) and sometimes we don't because we want to really work it like Aristotle would want us (who cares about what you think; what are the facts in nature?).
Through an iterative process of showing these blue and bluish items to people and having them identify the items as blue or not blue, or even more or less blue, we can identify a prototypically blue object, one which a statistically significant portion of our group of people would consider blue. Note that there is error inherent in this process, we never assume it's perfect, we just want it to work well enough that we have confidence in it. This prototypical blue object then would serve as our measure for what "blue" is. Many people consider the color of the sky as this standard (although I've lived in places where the sky was more white than blue most of the time).
So now we have our prototypical object (reality), which represents blue (the concept) that we can then use as a standard (measure) for what is "blue". The cool thing about this process, is that it doesn't stop there. We continually validate the prototypical object as being representative of blue in reality each time we use it. We can even enhance it representativeness as we go along if we find a more prototypically blue object. The expectation is that we will always use the most prototypical representation of the concept, and if for some reason someone doesn't, the peer review process kicks in, and they're corrected.
Another caveat is that the process, clearly, works better for things that are more easily representative and observable by others, and/or things that we've established a greater amount of public language about. So for example, we are much more likely to have widespread agreement on what a chair is than what blue is, and in turn what blue is than what pain is.
I guess another way to connect all the concepts together would be to suggest that Popper's philosophizing lead to a system whereby language could be migrated from one that is more of a private language to one that is more of a public language. Or am I not understanding that argument well? Admittedly, I'm not as familiar with it as any other poster in this thread. By a long shot.
HG