I would have to say that interpretation is totally up to the listener. Hey, why not? As far as I'm concerned, a song can mean whatever you, the fan, wants it to mean (whether that was the original intention of the author or not). So, if you want the "blue" in each song to convey the same or similar images, thoughts, etc. then sure!
It's like when we do art interpretation in my class. Invariably, after studying a piece of art for twenty minutes and then writing down what they think it is about, someone says, "Well, how can I know? I have to ask the artist." Who, in most cases, is dead. It's nice to be able to attach your own meaning to something and not be locked into what "the artist" may or may not have wanted you to know or come away with. I tell the kids, "There is no wrong answer." When they are set free to think in this way, the response is beautiful.
But it never hurts to find out what the artist had in mind about their own work. Obviously I have my own ideas about these songs and stuff but I like to know what they were intended to mean. But that doesn't affect my view of what I think it is.